Means and methods for site-specific functionalization of polypeptides

ABSTRACT

The present invention provides means and methods for equipping a polypeptide of interest at its C-terminus with a versatile adaptor amino acid that allows the functionalization of the polypeptide of interest.

BACKGROUND

Protein engineering has become a widely used tool in many areas ofprotein biochemistry. For example, protein fusion tags are indispensabletools used to improve recombinant protein expression yields, enableprotein purification, and accelerate the characterization of proteinstructure and function. Solubility-enhancing tags, geneticallyengineered epitopes, and recombinant endoproteases have resulted in aversatile array of combinatorial elements that facilitate proteindetection and purification. However, also protein modifications are ofimportance to study structure and function relationships.

Instead of the random labeling of amino acids, such as lysine residues,methods have been developed to (sequence) specific label proteins. Nextto chemical modifications, tools to integrate new chemical groups forbioorthogonal reactions/modifications or chemoselective modificationshave been applied. Alternatively, proteins can also be selectivelymodified by enzymes. By modifying existing amino acids or introducingnon-natural amino acids, proteins can be manipulated at the single aminoacid level. Several methods involving the site-specific modification ofproteins have been reported in the last decade. This allows the spatialand temporal control of proteins in vivo, as well as single moleculetracking. Modifications are introduced during protein translation, aspost translational modification or chemically, after protein isolation.

After translation, almost all proteins require post-translationalmodifications (PTMs) before becoming mature. The oxidation of cysteinesis a common PTM and is important for protein folding and stability.Other PTMs increase the functional diversity of proteins by themodification of amino acids including phosphorylation, glycosylation,ubiquitination, nitrosylation, methylation, acetylation and prolinecis-trans isomerization. Site-specific enzymatic PTMs are of particularinterest since they can be used to manipulate and/or study proteins.

Examples for PTM are membrane associated modifications facilitated byfarnesyl- and N-myristoyltransferases. In another approach the nativeformylglycine generating enzyme (FGE) is used to introduce formylglycinein both prokaryotes and eukaryotes. The aldehyde tagged protein can bereadily functionalized with aminooxy- or hydrazide-functionalizedbiomolecules. Besides the modification of other proteins, some enzymescan be used for self-modification such as human O6-alkylguanine-DNAalkyl transferase (hAGT), cutinase and halo alkane dehalogenase.

A straightforward class of enzymes for modifying proteins aftertranslation are the ligases. Biotin ligase (BirA) was shown to acceptalso a ketone isostere of biotin as a cofactor. Ligation of this biotinanalog to proteins bearing the 15-amino-acid acceptor peptide (AP) wasdemonstrated in vitro and in vivo, followed by subsequentketone-hydrazine conjugation. Second, the microbial lipoic acid ligase(LplA) was used to specifically attach an alkyl azide onto proteins withan engineered LplA acceptor peptide (LAP). Another ligase is theintein-based protein ligation system. A prerequisite for thisintein-mediated ligation method is that the target protein is expressedas a correctly folded fusion with the intein, which may be challenging.

Another set of post-translational modifications is performed byphosphopantetheinyl transferases (PPTases). PPTases transfer aphosphopantetheinyl (P-pant) group through a phosphodiester bond ontopeptidyl/acyl carrier protein (PCP/ACP) domains. These typically 80-120residues long domains are present on nonribosomal peptide synthetases(NRPSs), polyketide synthases (PKSs), and fatty acid synthases (FASs).Interestingly, orthogonal fluorescent labeling of cell surface receptorswas demonstrated by using the PPTases Sfp and AcpS selective peptidetags.

Instead of exploring the chemical space in which biomolecules can bemodified by functional groups and subsequently incorporated in proteinsof interest, some general applicable enzymatic modifications preexist innature. Transpeptidation is, for example, catalyzed by sortases, atranspeptidase from Staphylococcus aureus, has emerged as a generalmethod for derivatizing proteins with various types of modifications.For conventional sortase modifications, target proteins are engineeredto contain a sortase recognition motif (LPXT) near their C-termini. Whenincubated with synthetic peptides containing one or more N-terminalglycine residues and a recombinant sortase, these artificial sortasesubstrates undergo a transacylation reaction resulting in the exchangeof residues C-terminal to the threonine residue with the syntheticoligoglycine peptide, resulting in the protein C-terminus being ligatedto the N-terminus of the synthetic peptide (WO 2013/003555).

Other techniques for protein engineering are based on chemoselectiveligation and incorporation of modified amino acid residues which mayserve as joint connection for the addition of functional moieties suchas drugs, dyes, etc. (Hackenberger and Schwarzer (2008), Angew. Chem.Ed. 47, 10030-10074).

Site-specific modification of proteins has emerged as powerful tool tostudy proteins at the single amino acid level. However, it is stillchallenging to engineer a protein after its translation, i.e., makingpost-translational modifications, since the reactions required tofunctionalize a translated protein, e.g. by adding a label at only onespecific amino acid are oftentimes difficult, time- andmaterial-consuming. Thus, there is still a demand for engineering aprotein so as to have readily available a protein with an adaptor thatallows a functionalization of said polypeptide.

The present application satisfies this demand by the provision of meansand methods for equipping a protein of interest with a C-terminaladaptor amino acid which allows a functionalization of said protein asdescribed herein below, characterized in the claims and illustrated bythe appended Examples and Figures.

The inventors have unexpectedly discovered that, in contrast to thewidespread prejudice in the prior art, tubulin-tyrosine ligase (TTL) isable to tyrosinate polypeptides modified to comprise a TTL-recognitionsequence. In other words, the present inventors transferred action ofTTL out of its context, i.e., its action on tubulin and showed that TTLis also active on heterologous substrates such as peptides orpolypeptides that merely contain a TTL recognition sequence at theirC-terminus, but are otherwise not structurally related to a tubulin,i.e., non-tubulin peptides or polypeptides. As explained in more detailbelow, the prevailing view in the prior art was that TTL merely acts ontubulin polypeptides, while the present inventors proofed much to theirsurprise the opposite (see Examples 8 and 8.1). TTL is active onheterologous polypeptides and equips them with a tyrosine or tyrosinederivative which acts as versatile adaptor for, e.g., moieties thatfunctionalize a polypeptide.

It was also surprising for the present inventors to observe that withinthe “artificial”, (i.e. non-natural environment and non-tubulinpolypeptides as substrate for TTL) in which they used TTL to tyrosinatepolypeptides that TTL even introduced a tyrosine derivative to theC-terminus of a polypeptide of interest, which is different fromtubulin. Thus, TTL is able to incorporate a tyrosine derivative into anon-tubulin polypeptide in a non-natural environment, while it wastaught in the art that TTL is strictly tubulin dependent.

Accordingly, this finding enables the attachment of a tyrosine ortyrosine derivative to a plethora of different polypeptides, and, byfurther addition of other moieties, opens new perspectives for research,diagnosis, and treatment. Hence, by making use the action of TTL, it ispossible to functionalize a polypeptide of interest (POI), sincetyrosine or a tyrosine derivative added by TTL to the C-terminus of aprotein having a TTL recognition sequence allows coupling of moieties byway of a non-peptidic bond which serve, e.g. as labels, enzymes, drugs,etc. Thus, having recognized and proofed that TTL is active onheterologous substrates such as peptides or polypeptides that merelycontain a TTL recognition sequence at their C-terminus, but areotherwise not structurally related to a tubulin, makes TTL a tool forequipping a POI with a tyrosine or tyrosine derivative that acts asversatile adaptor that itself is connected with moieties whichfunctionalize a POI for, e.g. research, diagnosis, and treatment.

Tubulin-tyrosine ligase (TTL), which was first isolated from brainextracts in 1977, catalyzes the post-translational retyrosination ofdetyrosinated α-tubulin. It has a marked degree of sequence conservationfrom echinoderms to humans, and exhibits >96% identity among mammalianorthologs (Szyk, Deaconsecu and Piszczek). Remarkably, the enzyme isindispensable for cell and organism development, and TTL suppression hasbeen linked to cell transformation and correlates with poor prognosis inpatients suffering from diverse forms of cancers (Prota, Magiera andKujpers).

In nature, TTL plays an important role in recurrent α-tubulindetyrosination/tyrosination cycles. The high substrate specificity ofTTL has early been acknowledged. Even before TTL had been isolated,Arce, Hallak and Rodriguez reported in 1975 that when brain extracts areincubated with radioactive tyrosine, the label is only incorporated intoa tubulin. In 1994, Rüdiger et al. assessed TTL substrate requirementsby using a variety of synthetic peptides corresponding to the C-terminalsequence of α-tubulin.

Interestingly, the prejudice that αβ-tubulin or fragments thereof werethe only substrate accepted by TTL for efficient tyrosination persistedin the prior art. In consequence, research on TTL activity was, in thefollowing years, confined to assess whether TTL would accept tyrosinederivatives and attach them to the αβ-tubulin heterodimer. For example,Kalisz et al. (2000), Biochim Biophys Acta 1481: 131-138 pioneered ingenerating recombinant TTL in E. coli. The recombinant TTL exhibitedsimilar catalytic properties as the mammalian brain tissue derivedenzyme and was capable of covalently incorporating nitrotyrosine intothe C-terminus of α-tubulin in vitro, albeit at 35-fold lower affinitythan for tyrosine. Recently, Banerjee et al. (2010), ACS chemicalbiology 5: 777-785 successfully employed the TTL to conjugate afluorescent label to αβ-tubulin. The authors developed a two steplabeling systems under mild conditions and used 3-formyltyrosine as aTTL substrate and attached it to the C-terminus of a tubulin.Subsequently, 7-hydrazino-4-methyl coumarin was added by hydrazoneformation to the modified tubulin as a fluorescent label under mildconditions, allowing fluorescently labeled tubulin to retain its abilityto assemble into microtubules. Again, the authors here emphasize thatthe only TTL substrate is the C-terminus of α tubulin with the minimalrequirement of EE as the last amino acids.

However, the idea to use TTL for attaching a tyrosine (or derivativethereof) to polypeptides other than tubulin did not evolve—presumablybecause preceding studies implied that a unique interaction between TTLand αβ-tubulin was required in order to enable tyrosination. Recently,the prejudice has been confirmed by two studies conducted by (Szyk,Deaconsecu and Piszczek) and (Prota, Magiera and Kujpers).

Szyk et al. (2011), Nature Struc Mol Biol 18(11): 1250-1259 determinedthe crystal structure of frog TTL. The study revealed that TTL has anelongated shape and is composed of an N-terminal domain, a centraldomain and a C-terminal domain, which together form the active site ofthe enzyme. The authors further reported that TTL recognizes tubulin bya bipartite strategy. It engages the tubulin tail through low-affinity,high-specificity interactions, and co-opts what is otherwise ahomo-oligomerization interface to form a tight hetero-oligomeric complexwith the tubulin body. Put it differently, Szyk et al. clearly teachthat TTL is highly specific for tubulin and for its action it requires atight interplay with tubulin.

Prota et al. (2013), J Cell Biol 200(3): 259-270 recently revealed thestructural basis of TTL-tubulin interaction and tubulin tyrosination.Interestingly, based on the structural information obtained during thestudy, the authors conclude that a characteristic bipartite a ptubulin-TTL binding and a tubulin tail-TTL binding mode account for thehigh specificity of TTL for a tubulin. The authors state that thecomplex bipartite interaction mode observed between tubulin and TTLreveal how the enzyme has specifically evolved to recognize and modifytubulin; they virtually preclude that the enzyme modifies additionalsubstrates.

In sum, the prior art implies that the unique interaction between TTLand its substrate αβ tubulin is an indispensable prerequisite fortyrosination. Clearly, the finding of the present invention, allowingthe tyrosination by TTL of virtually any polypeptide carrying a TTLrecognition motif, was unexpected. The fact that adding or introducing aTTL recognition sequence into any functional polypeptide would sufficein order to render it a suitable TTL substrate was clearly and could notbe foreseen. All the more, apart from taking action on heterologouspolypeptides, the fact that TTL uses in a heterologous context eventyrosine derivatives as shown by the present inventors (see Examples 5and 8.2) could not at all have been expected and highlights thenon-obviousness of the present invention.

SUMMARY

The present invention provides a method for the production of apolypeptide comprising

(a) introducing or adding at the C-terminus of a polypeptide arecognition sequence for tubulin tyrosine ligase;

(b) optionally contacting the polypeptide obtained in step (a) in thepresence of tubulin tyrosine ligase and a tyrosine derivative underconditions suitable for the tubulin tyrosine ligase to tyrosinate saidpolypeptide with said tyrosine derivative; and

(c) optionally conjugating a moiety to said tyrosinated polypeptideobtained in step (b).

Step (c) is also envisaged to be a preferred step of the above method.Hence, in a preferred embodiment, said above method of the presentinvention further comprises step (c) conjugating a moiety to saidtyrosinated polypeptide obtained in step (b).

The present invention also provides a polypeptide which is obtainable bythe methods, particularly by said above method of the present invention.Such polypeptide obtainable by the methods of the present invention andapplied therein may advantageously have a length of more than 19 aminoacids and/or may be a polypeptide other than tubulin.

The present invention, as an alternative to the afore described method,provides a method for the production of a polypeptide, comprising

(a′) introducing or adding at the C-terminus of a polypeptide arecognition sequence for tubulin tyrosine ligase; and

(b′) contacting the polypeptide obtained in step (a′) in the presence oftubulin tyrosine ligase and a tyrosine derivative conjugated to a moietyunder conditions suitable for the tubulin tyrosine ligase to tyrosinatesaid polypeptide with said tyrosine derivative conjugated to saidmoiety.

The present invention also provides a polypeptide obtainable by saidalternative method of the present invention. Such a polypeptide may, forexample, also be tubulin, since the prior art did not provide tubulincomprising a tyrosine derivative and a further moiety, preferably amoiety as described herein.

The recognition sequence for tubulin tyrosine ligase of a polypeptidethat is subjected to a method of the present invention and that may alsobe comprised by a polypeptide of the present invention may preferablyhave at least the amino acid sequence X₁X₂X₃X₄ (SEQ ID No: 11), whereinX₁ and X₂ is any amino acid, X₃ is E, D or C and X₄ is E.Advantageously, X₂ may be G, S, A, V, or F and/or X₁ may be E, D, A, K,or P. The recognition sequence may be EGEE (SEQ ID No. 2),VDSVEGEGEEEGEE (SEQ ID No. 3), SVEGEGEEEGEE (SEQ ID No. 4), SADGEDEGEE(SEQ ID No. 5), SVEAEAEEGEE (SEQ ID No. 6), SYEDEDEGEE (SEQ ID No. 7),or SFEEENEGEE (SEQ ID No. 8).

The polypeptide that is produced and thus obtainable by the methods ofthe invention may comprise a linker sequence preceding the recognitionsequence of tubulin tyrosine ligase.

The moiety that may be conjugated to a tyrosinated polypeptide by way ofthe methods of the present invention and that may be comprised by apolypeptide of the present invention may a carrier, a polypeptide, adetectable label, a chemical compound, a nucleic acid, a carbohydrate,or a lipid. Such a polypeptide that is conjugated to a tyrosinatedpolypeptide may be an antibody or fragment thereof selected from thegroup consisting of a monoclonal antibody, chimeric antibody, humanizedantibody, human antibody, scFv, a DART, domain antibody, nanobody, anadnectin, an affibody, an anticalin, a DARPin, or an aptamer. Such adetectable label may comprise a fluorophore, an enzyme (peroxidase,luciferase), a radioisotope, a PET-tracer, a fluorescent protein, or afluorescent dye. Such a chemical compound may be a small molecule, apolymer, such as a synthetic polymer (PEG) or a therapeutic agent. Sucha nucleic acid may be DNA, RNA, or an aptamer.

Suitable conditions applied in the methods for producing a polypeptideof the invention may comprise a buffer containing a nucleosidetriphosphate, such as ATP, potassium chloride, magnesium chloride, areducing agent such as DTT.

A tyrosine derivative that is applied in the methods of the inventionand also comprised by a polypeptide of the invention may contain anunnatural (non-natural) functional group for a chemoselective orbioorthogonal modification however, it may alternatively contain anatural functional group for a chemoselective or bioorthogonalmodification. Sometimes, when used herein, a tyrosine derivative thatcontains an unnatural (non-natural) functional group for achemoselective or bioorthogonal modification is also referred to as a“click chemistry handle”. This unnatural functional moiety may beselected from the group consisting of terminal alkyne, azide, strainedalkyne, diene, dienophile, alkoxyamine, carbonyl, phosphine,phosphonite, phosphite, hydrazide, thiol, tetrazine, alkene,cyclooctyne, electron-withdrawing substituents such as halogens, e.g. F,Br, Cl, I, phenol-derivatives (e.g. OTs, ONs, OTf), nitriles (CN),carbonyls (CO), or nitro groups (NO2).

The tyrosine derivative applied in the methods of the invention may besubstituted with the above mentioned functional groups at positions 2, 3and 4 as well as at the benzylic position. The functional groups may beconnected directly at the above mentioned positions or via a spacer,such as an alkyl spacer in between. By way of example, the tyrosinederivative may be a 3-substituted or 4-substituted tyrosine, such as 3-or 4-substituted tyrosine derivative is 3-nitrotyrosine,3-aminotyrosine, 3-azidotyrosine, 3-formyltyrosine, 3-acetyltyrosine, or4-aminophenylalanine.

A polypeptide that is provided herein which is, for example, obtainableby the present invention has at its C-terminus a recognition sequencefor tubulin tyrosine ligase (TTL) which has preferably at least theamino acid sequence X₄X₃X₂X₁, wherein X₂ is E, D or C and X₁ is E.Advantageously, such a polypeptide is modified to introduce or add saidrecognition sequence Said polypeptide has advantageously biologicalactivity.

X₄ can be E, D, A, K, or P. X₃ can be G, S, A, V, or F. X₂ may also beG, S, A, V, or F. X₁ may also be E, D, A, K, or P. Preferably, therecognition sequence may be EGEE (SEQ ID No. 2), VDSVEGEGEEEGEE (SEQ IDNo. 3), SVEGEGEEEGEE (SEQ ID No. 4), SADGEDEGEE (SEQ ID No. 5),SVEAEAEEGEE (SEQ ID No. 6), SYEDEDEGEE (SEQ ID No. 7), or SFEEENEGEE(SEQ ID No. 8).

The polypeptide can comprise a linker sequence preceding the recognitionsequence of tubulin tyrosine ligase.

In the polypeptide of the invention, a tyrosine derivative can becovalently bonded to said recognition sequence. Said tyrosine derivativemay contain an unnatural (non-natural) functional group for achemoselective or bioorthogonal modification however, it mayalternatively contain a natural functional group for a chemoselective orbioorthogonal modification. This unnatural functional moiety may beselected from the group consisting of terminal alkyne, azide, strainedalkyne, diene, dienophile, alkoxyamine, carbonyl, phosphine,phosphonite, phosphite, hydrazide, thiol, tetrazine, alkene,cyclooctyne, electron-withdrawing substituents such as halogens, e.g. F,Br, Cl, I, phenol-derivatives (e.g. OTs, ONs, OTf), nitriles (CN),carbonyls (CO), or nitro groups (NO2). The tyrosine derivative may besubstituted with the above mentioned functional groups at positions 2, 3and 4 as well as at the benzylic position. The functional groups may beconnected directly at the above mentioned positions or via a spacer,such as an alkyl spacer in between. By way of example, the tyrosinederivative may be a 3-substituted or 4-substituted tyrosine, such as 3-or 4-substituted tyrosine derivative is 3-nitrotyrosine,3-aminotyrosine, 3-azidotyrosine, 3-formyltyrosine, 3-acetyltyrosine, or4-aminophenylalanine.

Further, a moiety can be conjugated to said tyrosine derivative. Saidmoiety can be a carrier, a polypeptide, a detectable label, a chemicalcompound, a nucleic acid, a carbohydrate, or a lipid. The polypeptidecan be, in particular, an antibody or fragment thereof selected from thegroup consisting of a monoclonal antibody, chimeric antibody, humanizedantibody, human antibody, scFv, a DART, domain antibody, nanobody, anadnectin, an affibody, an anticalin, a DARPin, or an aptamer. Thedetectable label may comprise a fluorophore, an enzyme (peroxidase,luciferase), a radioisotope, a fluorescent protein, or a fluorescentdye. The chemical compound can be a small molecule, a polymer, such as asynthetic polymer (PEG) or a therapeutic agent. The nucleic acid can beDNA, RNA, or an aptamer.

Also provided by the present invention is a diagnostic compositioncomprising a polypeptide that is, for example, obtainable by the methodsof the present invention.

Furthermore, also provided is a pharmaceutical composition a polypeptidethat is, for example, obtainable by the methods of the presentinvention.

The present invention moreover provides a kit comprising means forperforming the method of the present invention. The kit may comprise anexpression vector which allows expression of a protein of interest fusedat its C-Terminus to a recognition sequence for tubulin tyrosine ligase,tubulin tyrosine ligase and a tyrosine derivative.

Also provided by the present invention is the use of tubulin tyrosineligase for tyrosinating a polypeptide other than tubulin having at itsC-terminus a recognition sequence for tubulin tyrosine ligase.

A method for installing a chemistry handle to the C-terminus of apolypeptide other than tubulin is also provided herein, said methodcomprising:

(a) providing a polypeptide having at its C-terminus a tubulin tyrosineligase recognition sequence; and

(b) contacting the polypeptide of step (a) in the presence of tubulintyrosine ligase and a tyrosine derivative containing a chemistry handleunder conditions suitable for the tubulin tyrosine ligase to tyrosinatesaid polypeptide with said tyrosine derivative.Said method may optionally further comprise the step of conjugating amoiety as described herein to said tyrosinated polypeptide obtained instep (b).

The present invention also provides the use of tubulin tyrosine ligasefor installing a chemistry handle to the C-terminus of a polypeptideother than tubulin, said polypeptide having at its C-terminus a tubulintyrosine ligase recognition sequence.

It must be noted that as used herein, the singular forms “a”, “an”, and“the”, include plural references unless the context clearly indicatesotherwise. Thus, for example, reference to “a reagent” includes one ormore of such different reagents and reference to “the method” includesreference to equivalent steps and methods known to those of ordinaryskill in the art that could be modified or substituted for the methodsdescribed herein.

Unless otherwise indicated, the term “at least” preceding a series ofelements is to be understood to refer to every element in the series.Those skilled in the art will recognize, or be able to ascertain usingno more than routine experimentation, many equivalents to the specificembodiments of the invention described herein. Such equivalents areintended to be encompassed by the present invention.

The term “and/or” wherever used herein includes the meaning of “and”,“or” and “all or any other combination of the elements connected by saidterm”.

The term “about” or “approximately” as used herein means within 20%,preferably within 10%, and more preferably within 5% of a given value orrange. It includes, however, also the concrete number, e.g., about 20includes 20.

The term “less than” or “greater than” includes the concrete number. Forexample, less than 20 means less than or equal to. Similarly, more thanor greater than means more than or equal to, or greater than or equalto, respectively.

Throughout this specification and the claims which follow, unless thecontext requires otherwise, the word “comprise”, and variations such as“comprises” and “comprising”, will be understood to imply the inclusionof a stated integer or step or group of integers or steps but not theexclusion of any other integer or step or group of integer or step. Whenused herein the term “comprising” can be substituted with the term“containing” or “including” or sometimes when used herein with the term“having”.

When used herein “consisting of” excludes any element, step, oringredient not specified in the claim element. When used herein,“consisting essentially of” does not exclude materials or steps that donot materially affect the basic and novel characteristics of the claim.

In each instance herein any of the terms “comprising”, “consistingessentially of” and “consisting of” may be replaced with either of theother two terms.

It should be understood that this invention is not limited to theparticular methodology, protocols, material, reagents, and substances,etc., described herein and as such can vary. The terminology used hereinis for the purpose of describing particular embodiments only, and is notintended to limit the scope of the present invention, which is definedsolely by the claims.

All publications and patents cited throughout the text of thisspecification (including all patents, patent applications, scientificpublications, manufacturer's specifications, instructions, etc.),whether supra or infra, are hereby incorporated by reference in theirentirety. Nothing herein is to be construed as an admission that theinvention is not entitled to antedate such disclosure by virtue of priorinvention. To the extent the material incorporated by referencecontradicts or is inconsistent with this specification, thespecification will supersede any such material.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1: Schematic illustration of the present invention. (A) Shown isthe natural reaction of Tubulin tyrosination catalyzed by TTL. TTLinteracts with a C-terminal TTL Reactive Motif (Tub-tag) and catalyzesthe ligation of a C-terminal tyrosine. (B) Shown is the engineeredreaction. The Tub-tag is recombinantly added to any protein of interest(POI). TTL catalyzes the C-terminal ligation of tyrosine and tyrosinederivatives that can be used for site-specific conjugation chemistry ofany reactive molecule.

FIG. 2: C-terminal ligation of 3-nitro-tyrosine (A, E), 3-azide-tyrosine(B, F), 3-formyl-tyrosine (C, G) and 3-iodo-tyrosine (D, H) to theα-tubulin derived, 14mer peptide. (A, B, C, D) The red line representsthe consumption of peptide, the blue line the formation of C-terminalfunctionalized peptide, the black line the formation of side product.The mean value of three replicate reactions is shown (SD). Quantitationof substrate and product was done via integration of peak. (E, F, G, H)HPLC-fluorescence traces that were taken at different time points of theTTL reaction with 3-nitro-tyrosine (E), 3-azide-tyrosine (F),3-formyl-tyrosine (G) and 3-iodo-tyrosine and peptide are shown. Thefluorescence peak corresponding to peptide (left) is getting smallerwithin time and a new peak, corresponding to C-terminal modifiedpeptide, is appearing.

FIG. 3: Mass spectrometric validation of the C-terminal ligation of3-formyl-tyrosine at the protein level (nanobody with C-terminalα-tubulin derived, 14mer peptide). An ESI MS/MS diagram of the nanobodyafter in gel digest using trypsin. The MS/MS diagram of the peptidecarrying the terminal 3-formyl-tyrosine residue is shown.

FIG. 4: (A) C-terminal attachment of a biotin-derivative to a nanobodyby oxime forming reaction. 3-formyl-L-tyrosine was enzymaticallyincorporated to the C-terminus of the nanobody. Thus, thesite-specifically incorporated aldehyde group was used to install biotinin an oxime forming reaction. The SDS-gel shows the untreated nanobodyin lane 1, the reaction where the nanobody was incubated with TTL and3-formyl-L-tyrosine (lane 2) and the reaction where the nanobody wasincubated with TTL alone (lane 2). Following the enzymatic reaction, thesamples were incubated with 20 eq. of the biotin. Selective labeling ofthe 3-formyl-L-tyrosine containing nanobody is shown. (B) C-terminalattachment of Alexa594 to a nanobody by hydrazone forming reaction.3-formyl-L-tyrosine was enzymatically incorporated to the C-terminus ofthe nanobody. Thus, the site-specifically incorporated aldehyde groupwas used to install a fluorophore, namely Alexa594, in a hydrazoneforming reaction. The SDS-gel shows the reaction of nanobody-Tub-tagwith TTL and 3-formyl-L-tyrosine (lane 1), the reaction wherenanobody-Tub-tag was incubated with TTL alone (lane 2) and the reactionwhere a nanobody without the Tub-tag peptide was used (lane 3).Following the enzymatic reaction, the three samples were incubated with30 eq. of fluorophore. Selective labeling of the 3-formyl-L-tyrosinecontaining nanobody is shown.

FIG. 5: Tub-tag labeling of proteins. (A) Chemoenzymatic labeling ofproteins by tubulin tyrosine ligase (TTL). Unnatural tyrosinederivatives are ligated to the C-terminus of a short recognition tag(Tub-tag) to serve as bioorthogonal handles for a site-specific chemicalmodification of a protein of interest (POI). (B) C-terminal addition of3-N₃-L-tyrosine to carboxyfluorescein labeled peptide (CF-Tub-tag).HPLC-fluorescence traces were taken at different time points of the TTLreaction. (C) The red line represents the consumption of CF-Tub-tag, theblue line the formation of C-terminally functionalized CF-Tub-tag-YN₃.The mean value and standard deviation (SD) of three replicate reactionsis shown. Quantitation of substrate and product was performed via peakintegration of b. (D) C-terminal addition of 3-formyl-L-tyrosine toCF-Tub-tag. HPLC-fluorescence traces were taken at different time pointsof the TTL reaction. (E) The red line represents the consumption ofCF-Tub-tag, the green line the formation of C-terminally functionalizedCF-Tub-tag-YCHO. The mean value and standard deviation (SD) of threereplicate reactions is shown. Quantitation of substrate and product wasperformed via peak integration of d.

FIG. 6: Principle and efficiency of TTL-mediated functionalization (A)Schematic illustration of TTL mediated incorporation of azide 3 followedby subsequent strain promoted azide-alkyne cycloaddition (SPAAC). (B)Incorporation of azide 3 to the C-terminus of GBP4 using differentratios of GBP4/TTL and reaction times (one and three hours) followed bySPAAC to a DBCO-biotin derivative. SDS-PAGE and western blot (anti-StrepAb-HRP) show efficient biotin labeling of GBP4 within one hour.

FIG. 7: Application of chemoenzymatically functionalized nanobodies (A)Schematic outline of immunoprecipitation of GFP with site-specificallybiotinylated GBP1. (B) Coomassie staining and western blot analysisshowing efficient and specific GFP pulldown. (C) Schematic outline ofthe site-specifically labeled GBP1-Alexa594 (D) Immunofluorescence withGBP1-Alexa594. Shown is a HeLa cell nucleus with the lamina co-labeledwith LaminB1-GFP and GBP1-Alexa594. Scale bar is 10 μm. (E) zoom regionof d. (F) A fluorescence intensity profile along the dotted line (shownin e) demonstrates high colocalization accuracy at subdiffractionresolution.

FIG. 8: Different tyrosine derivatives have been added to the C-terminusof the nanobody GBP4 using Tub-tag labeling. Tryptic digest followed byHPLC-MS/MS experiments revealed successful incorporation of (A)L-tyrosine, (B) 3-N₃-L-tyrosine, (C) 3-formyl-L-tyrosine, (D)3-NH₂-L-tyrosine and (E) 3-NO₂-L-tyrosine.

FIG. 9: Molecules used for bioorthogonal addition to C-terminal modifiednanobodies.

FIG. 10: Shown is the fluorescent labeling of GBP4 with sulfo-Cy5-DBCO.3-N₃-L-tyrosine was enzymatically incorporated to the C-terminus of GBP4using TTL. A following incubation with 30 eq. sulfo-Cy5-DBCO showsselective labeling of 3-N₃-L-tyrosine containing nanobody by strainpromoted azide-alkyne click reaction (SPAAC).

FIG. 11: Shown is the labeling of GBP4 with biotin-phosphine usingStaudinger-Ligation. 3-N₃-L-tyrosine was enzymatically incorporated tothe C-terminus of GBP4 using TTL. A following incubation with 40 eq.Biotin-phosphine shows selective labeling of 3-N₃-L-tyrosine containingnanobody by Staudinger-Ligation.

FIG. 12: Shown is the PEGylation of GBP4 with tris(PEG750)phosphite (14)by Staudinger-Phosphite reaction. 3-N₃-L-tyrosine was enzymaticallyincorporated to the C-terminus of GBP4 using TTL. A following incubationwith 40 eq. phosphite shows selective labeling of 3-N₃-L-tyrosinecontaining nanobody by Staudinger Ligation.

FIG. 13: Shown is the labeling of GBP4 with Alexa594-hydrazide usinghydrazone forming reaction. 3-formyl-L-tyrosine was enzymaticallyincorporated to the C-terminus of GBP4 using TTL. A following incubationwith 30 eq. Alexa594-hydrazide shows selective labeling of3-formyl-L-tyrosine containing nanobody by aldehyde condensation.

FIG. 14: Shown is the labeling of GBP4 with biotin 15 using oximeforming reaction. 3-formyl-L-tyrosine was enzymatically incorporated tothe C-terminus of GBP4 using TTL. A following incubation with 30 eq. S2shows selective labeling of 3-formyl-L-tyrosine containing nanobody byaldehyde condensation.

FIG. 15: Shown is the site-specific labeling of the GFP specificnanobody GBP1 using Tub-tag labeling. (A) 3-N₃-L-tyrosine wasenzymatically incorporated to the C-terminus of GBP1 using TTL. Afollowing incubation with 30 eq. sulfo-Cy5-DBCO or 30 eq. biotin-DBCOshows selective labeling of 3-N₃-L-tyrosine containing nanobody bystrain promoted azide-alkyne click reaction (SPAAC). (B)3-formyl-L-tyrosine was enzymatically incorporated to the C-terminus ofGBP4 using TTL. A following incubation with 30 eq. Alexa594-hydrazideshows selective labeling of 3-formyl-L-tyrosine containing nanobody byaldehyde condensation.

FIG. 16: Confocal micrographs of HeLa cells transfected with GFP-PCNAfusions. Cells were labeled with anti-GFP (GBP1) conjugated to thefluorescent dye Alexa594 at 1:25. The DAPI, GFP and Alexa594 channels,as well as the overlay are shown. Scale bar: 5 μm.

FIG. 17: 3-N₃-L-tyrosine incorporation to the C-terminus of GBP4 inrelation to pH value is shown. Reactions were performed using a 10:1ratio GBP4:TTL at different pH values (5.0-9.0) for 3 h. Reactions werequickly cooled to 4° C., excess of 3-N₃-L-tyrosine removed via dialysis(at 4° C.) and SPAAC to DBCO-biotin performed. The yields were estimatedusing the software Image Lab (Bio-Rad, USA).

FIG. 18: 3-N₃-L-tyrosine incorporation to the C-terminus of GBP4 inrelation to 3-N₃-L-tyrosine concentration is shown. Reactions wereperformed using a 10:1 ratio GBP4:TTL at using different tyrosinederivative concentration (0.25-2 mM) for 1 h. Reactions were quicklycooled to 4° C., excess of 3-N₃-L-tyrosine removed via dialysis (at 4°C.) and SPAAC to DBCO-biotin performed. The yields were estimated usingthe software Image Lab (Bio-Rad, USA).

FIG. 19: 3-N₃-L-tyrosine incorporation to the C-terminus of GBP4 inrelation to reaction temperature is shown. Reactions were performedusing a 10:1 ratio GBP4:TTL at different temperatures for 1 h. Reactionswere quickly cooled to 4° C., excess of 3-N₃-L-tyrosine removed viadialysis (at 4° C.) and SPAAC to DBCO-biotin performed. The yields wereestimated using the software Image Lab (Bio-Rad, USA).

FIG. 20: The time correlation of 3-N₃-L-tyrosine incorporation to theC-terminus of GBP4 is shown. Reactions were performed using a 5:1 ratioGBP4:TTL at 37° C. Reactions were quickly cooled to 4° C. at specifictime-points, excess of 3-N₃-L-tyrosine removed via dialysis (at 4° C.)and SPAAC to DBCO-biotin performed. The yields were estimated using thesoftware Image Lab (Bio-Rad, USA).

FIG. 21: Coupling reactions

FIG. 22: One-Step Functionalization: TTL is able to add a tyrosinederivative, which is already coupled to a moiety, to a polypeptide.

FIG. 23. Lysate labeling and the application of chemoenzymaticallyfunctionalized nanobodies to protein enrichment and super resolutionmicroscopy.

a) Schematic outline of Tub-tag labeling of GFP in complex proteinmixtures (E. coli lysate). b) Coomassie staining and western blotanalysis showing the high selectivity of the tyrosine ligation andsubsequent biotinylation. (+: lysate treated with TTL, 3-N₃-L-tyrosine(1) and DBCO-biotin; C1: no 3-N₃-L-tyrosine (1) added; C2: lysatetreated with DBCO-biotin; C3: lysate; C4: purified GFP).c) Outline of the site-specific biotinylation of the GFP-bindingnanobody GBP1 and subsequent immunoprecipitation of GFP.d) Coomassie staining and western blot analysis showing efficient andspecific GFP pulldown (Mock GBP1-biotin: lysate lacking overexpressedGFP; GFP GBP1-biotin: beads loaded with GBP1 and lysate containing GFP;GFP control beads: beads without immobilized GBP1, I: input tostreptavidin beads; FT: flow-through; B: beads).e) Outline of the site-specific labeling of GBP1 with Alexa594f) Immunofluorescence with GBP1-Alexa594. Shown is a fixed HeLa cellnucleus with the lamina co-labeled with LaminB1-GFP and GBP1-Alexa594.Scale bar: 10 mm.g) expansion of the region highlighted in (d).h) Fluorescence intensity profile along the dotted line shown in (g)demonstrates high colocalization accuracy at sub-diffraction resolution.

FIG. 24 is a representation of the C-terminal incorporation of tyrosinederivatives to nanobodies.

FIG. 25 is a representation of the labelling of tyrosinated nanobodieswith biotin.

FIG. 26 is a representation of the labelling of a tyrosinated nanobodywith Alexa594®.

FIG. 27 is a representation of the one-step labeling of nanobody withbiotin 12.

FIG. 28 shows a plot, UV absorbance [mAU] on the y-axis versus time[min] on the x-axis for a LC-UV at 220 nm, 10 to 100% of acetonitrile inwater containing 0.1% TFA on a RP-C18 column.

DETAILED DESCRIPTION

The present inventors have, for the first time, acknowledged that TTLactivity is not limited to tubulin, but that TTL is capable oftyrosinating virtually any polypeptide having a C-terminal TTLrecognition motif in its amino acid sequence. This insight was by farnot self-evident—in the past, several studies investigated theprinciples of TTL-tubulin interaction, and came to the conclusion thatthe unique interaction of TTL and its substrate tubulin was essentialfor effective tyrosination. The insight that TTL could tyrosinate anyfunctional polypeptide carrying the specific recognition motif thereforecame as a surprise. It also came as a surprise that TTL can incorporatetyrosine derivatives at the C-terminus of a non-tubulin polypeptide.These two surprising findings open up new avenues for post-translationalmodifications of polypeptides, since the tyrosine derivative maycomprise a functional entity that allows its conjugation to whatevermoiety that can confer functionality to a polypeptide of interest thatis tyrosinated. The present invention therefore provides novelpolypeptides carrying a C-terminal TTL recognition sequence; which can,inter alia, act as TTL substrates to become tyrosinated and,advantageously further functionalized, since—as explained—the C-terminaltyrosine can beneficially be used as an “adapter” for attaching furthermoieties, e.g. fluorescent labels or therapeutic agents. Therefore, thepresent invention provides means and methods that hold considerablepotential for therapy, diagnosis and research.

Thus, the present invention provides a preferably recombinant orsynthetic polypeptide having at its C-terminus a recognition sequencefor tubulin tyrosine ligase (TTL). Said recognition sequence haspreferably at least the amino acid sequence X₄X₃X₂X₁, wherein X₂ is E, Dor C and X₁ is E. Said polypeptide is, as described herein, modified tointroduce or add said recognition sequence. Said polypeptide hasadvantageously biological activity. Said polypeptide has preferably alength of more than 19 amino acids, such as 20, 30, 40, 50, 60, 70, 80,90, 100, 150, 200, 250, or more amino acids in length.

The present invention also provides a method for the production of apolypeptide comprising

(a) introducing or adding at the C-terminus of a polypeptide arecognition sequence for tubulin tyrosine ligase;

(b) optionally contacting the polypeptide obtained in step (a) in thepresence of tubulin tyrosine ligase and a tyrosine derivative underconditions suitable for the tubulin tyrosine ligase to tyrosinate saidpolypeptide with said tyrosine derivative; and

(c) optionally conjugating a moiety to said tyrosinated polypeptideobtained in step (b).

Step (c) is also envisaged to be a preferred step of the above method.Hence, in a preferred embodiment, said above method of the presentinvention further comprises step (c) conjugating a moiety to saidtyrosinated polypeptide obtained in step (b).

As an alternative, the present in invention also provides a method forthe production of a polypeptide comprising

(a′) introducing or adding at the C-terminus of a polypeptide arecognition sequence for tubulin tyrosine ligase; and

(b′) contacting the polypeptide obtained in step (a′) in the presence oftubulin tyrosine ligase and a tyrosine derivative (already) conjugatedto a moiety under conditions suitable for the tubulin tyrosine ligase totyrosinate said polypeptide with said tyrosine derivative conjugated tosaid moiety.Said alternative method allows, so to say, a one-step functionalizationof a polypeptide in that tubulin tyrosine ligase tyrosinates apolypeptide into which a recognition sequence for tubulin tyrosineligase is introduced or added at its C-terminus with a tyrosinederivative conjugated to a moiety. Thus, said method, so to say,simplifies the functionalization in that no extra tyrosination step isrequired, where tubulin tyrosine ligase first adds a tyrosine derivativeto the C-terminus of a polypeptide into which a recognition sequence fortubulin tyrosine ligase is introduced or added in order to thenconjugate a moiety to said tyrosinated polypeptide. Rather, tubulintyrosine ligase was found by the present inventors to tyrosinate apolypeptide into which a recognition sequence for tubulin tyrosineligase is introduced or added at its C-terminus with a tyrosinederivative already conjugated to a moiety.

The terms “protein,” “peptide” and “polypeptide” are usedinterchangeably herein, and refer to a polymer of amino acid residueslinked together by peptide (amide) bonds. Said term also encompassesfragments of polypeptides. Said fragments have preferably biologicalactivity. Said fragments may have a length of 10, 20, 30, 40, 50, 60,70, 80, 90, 100, 150, 200, 250, 300, 350, 400, 450 or more amino acids.The terms refer to a protein, peptide, or polypeptide of any size,structure, or function, with the exception of tubulin. The term“tubulin” as used herein comprises any isoform (i.e., α-, β-, γ-, δ-,ε-, ζ-tubulin), mutant, variant or derivative of tubulin. As explainedherein, the finding of the present invention is, inter alia, thatpolypeptides other than tubulin, i.e. non-tubulin polypeptides aretyrosinated by TTL, provided they have a TTL recognition sequence. Inother words, the present inventors found that TTL is active onheterologous substrates, such as peptides or polypeptides that merelycontain a TTL recognition sequence at their C-terminus, but areotherwise not structurally related to a tubulin. “Heterologoussubstrate” means a peptide or polypeptide on which TTL is active by wayof tyrosination, but which is not a tubulin.

“A polypeptide or peptide other than tubulin” or “a non-tubulin peptideor polypeptide” encompasses a polypeptide which is not structurallyrelated to a tubulin polypeptide. Such a tubulin polypeptide haspreferably an amino acid sequence having a sequence identity of 60% ormore, such as 70%, 80%, 90% or 100%, to SEQ ID No. 1.

(SEQ ID NO. 1) MRECISIHVG QAGVQIGNAC WELYCLEHGI QPDGQMPSDK TIGGGDDSFN 50TFFSETGAGK HVPRAVFVDL EPTVIDEVRT GTYRQLFHPE QLITGKEDAA 100NNYARGHYTI GKEIIDLVLD RIRKLADQCT GLQGFLVFHS FGGGTGSGFT 150SLLMERLSVD YGKKSKLEFS IYPAPQVSTA VVEPYNSILT THTTLEHSDC 200AFMVDNEAIY DICRRNLDIE RPTYTNLNRL IGQIVSSITA SLRFDGALNV 250DLTEFQTNLV PYPRIHFPLA TYAPVISAEK AYHEQLSVAE ITNACFEPAN 300QMVKCDPRHG KYMACCLLYR GDVVPKDVNA AIATIKTKRT IQFVDWCPTG 350FKVGINYQPP TVVPGGDLAK VQRAVCMLSN TTAIAEAWAR LDHKFDLMYA 400KRAFVHWYVG EGMEEGEFSE AREDMAALEK DYEEVGVDSV EGEGEEEGEEThus, such tubulin polypeptides are preferably excluded from apolypeptide of the present invention that is tyrosinated and furthermodified by conjugation of a moiety to the tyrosine of the tyrosinatedpolypeptide or that is tyrosinated with a tyrosine derivative (already)conjugated to a moiety. A variety of sequence based alignmentmethodologies, which are well known to those skilled in the art, can beused to determine identity among sequences. These include, but notlimited to, the local identity/homology algorithm of Smith, F. andWaterman, M. S. (1981) Adv. Appl. Math. 2: 482-89, homology alignmentalgorithm of Peason, W. R. and Lipman, D. J. (1988) Proc. Natl. Acad.Sci. USA 85: 2444-48, Basic Local Alignment Search Tool (BLAST)described by Altschul, S. F. et al. (1990) J. Mol. Biol. 215: 403-10, orthe Best Fit program described by Devereau, J. et al. (1984) NucleicAcids. Res. 12: 387-95, and the FastA and TFASTA alignment programs,preferably using default settings or by inspection. Alternatively, analignment may be done manually/visually as follows: the percent identitybetween an amino acid sequence in question and the amino acid sequenceshown in SEQ ID No. 1 (reference sequence) is determined by pairwisealignment in such a way that the maximum identity is obtained betweenboth amino acid sequences. The identical amino acid residues betweenboth amino acid sequences are counted and divided by the total number ofresidues of the amino acid sequence shown in SEQ ID No. 1 (includingpositions that do not contain amino acid residues, e.g. one or moregaps) yielding the percentage of identity.

A protein, peptide, or polypeptide may refer to an individual protein ora collection of proteins. One or more of the amino acids in thepolypeptide may be modified, for example, by the addition of a chemicalentity such as a carbohydrate group, a hydroxyl group, a phosphategroup, a farnesyl group, an isofarnesyl group, a fatty acid group, alinker for conjugation, functionalization, a fusion partner forhalf-life extension, an affinity tags, such as a histidine tag,Flag-tag, streptavidin tag, strep II tag, an intein, a maltose-bindingprotein, an IgA or IgG Fc portion, protein A or protein G, and othermodifications. Other possible chemical modifications of the polypeptideinclude acylation or acetylation of the amino-terminal end or amidationor esterification of the carboxy-terminal end or, alternatively, onboth. The modifications may also affect the amino group in the sidechain of lysine or the hydroxyl group of threonine. Other possiblemodifications include, e.g., extension of an amino group withpolypeptide chains of varying length (e.g., XTEN technology orPASylation®), N-glycosylation, O-glycosylation, and chemical conjugationof carbohydrates, such as hydroxyethyl starch (e.g., HESylation®) orpolysialic acid (e.g., PolyXen® technology). Chemical modifications suchas alkylation (e. g., methylation, propylation, butylation), arylation,and etherification may be possible and are also envisaged. It is howeverpreferred that the modification does not abolish the capability of TTLto recognize the TTL recognition sequence and/or to tyrosinate thepolypeptide of the invention. A protein, peptide, or polypeptide mayalso be a single molecule or may be a multi-molecular complex. Aprotein, peptide, or polypeptide may be just a fragment of a naturallyoccurring protein or peptide, as long as it exhibits biological activityas defined herein.

The term “Tubulin tyrosine ligase”, abbreviated sometimes herein as TTL,encompasses polypeptides that are capable of tyrosinating polypeptides,i.e. covalently attaching a tyrosine or tyrosine derivative to apolypeptide. Preferably a TTL is capable of tyrosinating a polypeptideat the C-terminus of said polypeptide. For that action it is preferredthat said polypeptide comprises a recognition sequence for TTL. Saidterm encompasses TTLs from eukaryotes, preferably mammals, morepreferably from humans. A preferred TTL is shown in SEQ ID No: 12. Alsoencompassed by said term is a TTL that has 70%, 80%, 90% or 95% or moreidentity over its entire amino acid sequence with the amino acidsequence of the TTL shown in SEQ ID No: 12. Preferably, suchpolypeptides having an amino acid sequence which shares an identity asdescribed before have TTL activity. TTL activity can be tested as isknown in the art or described herein. The percentage of sequenceidentity can, for example, be determined herein as described above.Preferably the amino acid sequence shown in SEQ ID No: 12 is used asreference in a pairwise comparison. It is calculated as the percentageof numbers of “positives” (homologous amino acids) indicated as resultin the BLASTP program output divided by the total number of amino acidsselected by the program for the alignment.

The term “tyrosinating” in all its grammatical forms as used hereinmeans “covalently attaching a tyrosine or tyrosine derivative” to apolypeptide. Without wishing to be bound by a specific theory, it isenvisaged that the TTL adds a tyrosine or tyrosine derivative to theultimate C-terminal amino acid of the TTL recognition motif. Saidtyrosine or tyrosine derivative may already be conjugated to a moiety asdescribed herein. Conjugation of a moiety to a tyrosine or tyrosinederivative may be done as is known in the art or preferably be done asdescribed herein. Accordingly, it is thus also envisaged that the term“tyrosinating” encompassed that tubulin tyrosine ligase tyrosinates apolypeptide having a recognition sequences for TTL as described hereinwith a tyrosine or tyrosine derivative that is (already) conjugated witha moiety as described herein. This finding of the present inventors wasagain surprising in that TTL is able to use even tyrosine derivativesconjugated to large or bulky moieties (see FIG. 22).

The present invention preferably pertains to a “recombinant” or“synthetic” polypeptide. A “synthetic” polypeptide in the context of thepresent invention refers to a polypeptide that has been obtained bymethods of synthetic biology, including solid phase peptide synthesis(SPPS), prior thiol capture strategy, native chemical ligation (NCL),expressed protein ligation (EPL) and Staudinger ligation, and the O-acylisopeptide method. Such a synthetic polypeptide contains a TTLrecognition sequence that is introduced either by addition ormodification of the amino acid sequence of the synthetic polypeptide.The term “synthetic” polypeptide as used herein also includespolypeptides which have been treated to alter their natural amino acidsequence, e.g., by deamidation.

The term “recombinant” in the context of the present invention refers toa polypeptide that is genetically engineering, i.e., modified tointroduce or add a recognition sequence for TTL at the C-terminus of apolypeptide. It thus excludes such tubulins which naturally contain aTTL recognition sequence.

“Modified to introduce a recognition sequence” means that the amino acidsequence of a polypeptide is modified to introduce a TTL recognitionsequence, such as replacing or deleting, but not adding or inserting,one or more amino acids in order to build a TTL recognition sequence atthe C-terminus of a polypeptide.

“Modified to add a recognition sequence” means that the amino acidsequence of a polypeptide is modified to add a TTL recognition sequence,i.e., adding or inserting one or more amino acids in order to equip apolypeptide with a TTL recognition sequence at its C-Terminus.

Examples of polypeptides or proteins include recombinant or synthetichormones, cytokines and lymphokines, antibodies, receptors, adhesionmolecules, and enzymes as well as fragments thereof. A non-exhaustivelist of desired polypeptides include, e. g., recombinant or synthetichuman growth hormone, bovine growth hormone, parathyroid hormone,thyroid stimulating hormone, follicle stimulating hormone growth,luteinizing hormone; hormone releasing factor; lipoproteins;alpha-1-antitrypsin; insulin A-chain; insulin B-chain; proinsulin;calcitonin; glucagon; molecules such as renin; clotting factors such asfactor VIIIC, factor IX, tissue factor, and von Willebrands factor;anti-clotting factors such as Protein C, atrial natriuretic factor, lungsurfactant; a plasminogen activator, such as urokinase or human urine ortissue-type plasminogen activator (t-PA); bombesin; thrombin;hemopoietic growth factor; tumor necrosis factor-alpha and -beta;enkephalinase; RANTES (regulated on activation normally T-cell expressedand secreted); human macrophage inflammatory protein (MIP-1-alpha); aserum albumin such as human serum albumin; mullerian-inhibitingsubstance; relaxin A- or B-chain; prorelaxin; mousegonadotropin-associated peptide; DNase; inhibin; activin; receptors forhormones or growth factors; integrin; protein A or D; rheumatoidfactors; a neurotrophic factor such as bone-derived neurotrophic factor(BDNF), neurotrophin-3, -4, -5, or -6 (NT-3, NT-4, NT-5, or NT-6),growth factors including vascular endothelial growth factor (VEGF),nerve growth factor such as NGF-; platelet-derived growth factor (PDGF);fibroblast growth factor such as aFGF, bFGF, FGF-4, FGF-5, FGF-6;epidermal growth factor (EGF); transforming growth factor (TGF) such asTGF-alpha and TGF-beta, including TGF-pl, TGF-p2, TGF-p3, TGF-p4, orTGF-p5; insulin-like growth factor-I and -II (IGF-I and IGF-11); des(1-3)-IGF-I (brain IGF-I), insulin-like growth factor binding proteins;CD proteins such as CD-3, CD-4, CD-8, and CD-19; erythropoietin;osteoinductive factors; immunotoxins; a bone morphogenetic protein(BMP); an interferon such as interferon-alpha, -beta, and -gamma; colonystimulating factors (CSFs), e.g., M-CSF, GM-CSF, and G-CSF; interleukins(ILs), e.g., IL-1 to IL-10; superoxide dismutase; erythropoietin; T-cellreceptors; surface membrane proteins e.g., HER2; decoy acceleratingfactor; viral antigen such as, for example, a portion of the AIDSenvelope; transport proteins; homing receptors; addressins; regulatoryproteins; antibodies; chimeric proteins such as immunoadhesins andfragments of any of the above-listed polypeptides.

The polypeptide of the invention is modified to comprise a recognitionsequence for tubulin-tyrosine ligase (TTL) at its C-terminus, comprisingat least the amino acid sequence X₄X₃X₂X₁. The term “recognitionsequence” or “recognition motif” are used interchangeably herein andrefer to a stretch of amino acids that is recognized by the TTL. Suchrecognition sequences are known in the art; see, e.g., Ruediger et al.(1994), Eur. J. Biochem. 220, 309-320 or Prota e al. (2013), J. Cell.Biol. 200, No. 3, 259-270. Moreover, the skilled person can easily testwhether or not an amino acid sequence of interest is a TTL recognitionsequence by applying, e.g., the assay “Tyrosination of peptides by TTL”described in Ruediger et al., “Recognized” by the TTL includes bindingof the TTL to the recognition motif. The recognition motifadvantageously comprises at least 4 amino acids which are designated X₄,X₃, X₂ and X₁ herein. In general, “X” can denote any amino acid unlessindicated otherwise herein. Amino acids include includes but is notlimited to the twenty “standard” amino acids: isoleucine (Ile, I),leucine (Leu, L), lysine (Lys, K), methionine (Met, M), phenylalanine(Phe, F), threonine (Thr, T), tryptophan (Trp, W), valine (Val, V),alanine (Ala, A), asparagine (Asn, N), aspartate (Asp, D), cysteine(Cys, C), glutamate (Glu, E), glutamine (Gln, Q), glycine (Gly, G),proline (Prol, P), serine (Ser, S), tyrosine (Tyr, Y), arginine (Arg, R)and histidine (His, H). The present invention also includes, withoutlimitation, D-configuration amino acids, β-amino acids, amino acidshaving side chains as well as all non-natural amino acids known to oneskilled in the art. X₁ refers to the ultimate C-terminal amino acid inthe polypeptide, X₂ to the second to the last, and so on. X₁ is E, andX₂ is selected from E, D or C. X₃ is preferably G, S, A, V, or F,whereas X₄ is preferably selected from E, D, A, K or P. In someembodiments, X₅ (i.e. the next amino acid towards the N-terminus of X₄)is selected from E, A and V. In some embodiments, X₆ (i.e. the aminoacid following X₅) can be selected from E, A, K and G. In general, anycombination of X₁ and X₂ is conceivable which does not abolish theability of the TTL to recognize the respective recognition motif. TheTTL recognition sequence introduced in or added to the polypeptide ofthe invention can for example be EGEE (SEQ ID No. 2). In one particularembodiment, the TTL recognition sequence is VDSVEGEGEEEGEE (SEQ ID No.3, sometimes also referred to herein as TTL reactive motif),SVEGEGEEEGEE (SEQ ID No. 4), SADGEDEGEE (SEQ ID No. 5), SVEAEAEEGEE (SEQID No. 6), SYEDEDEGEE (SEQ ID No. 7), or SFEEENEGEE (SEQ ID No. 8). Ingeneral, any recognition sequence is envisaged wherein X₁ is E and X₂ isE, D or C, which is recognized by the TTL.

The term “having biological activity” as used herein means that apolypeptide has a specific functionality. For example, if thepolypeptide of the invention is a modified antibody, “having biologicalactivity” can mean, e.g., having antigen-binding activity. If thepolypeptide of the invention is a modified enzyme, “having biologicalactivity” can mean, e.g., having enzymatic activity.

The polypeptide can comprise a linker sequence preceding the recognitionsequence of tubulin tyrosine ligase. A “linker sequence” (also referredto as a “spacer sequence”) is an amino acid sequence that is introducedbetween the polypeptide of the invention and the TTL recognitionsequence, so as to connect the polypeptide and the TTL recognitionsequence. A linker sequence can for example be required in order toallow accurate folding of the polypeptide of the invention, and/or toensure flexibility and accessibility of the TTL recognition sequence.There are a great variety of possible linker sequences and it is withinthe knowledge of the person skilled in the art to choose a suitablelinker sequence based on, e.g., the size, sequence and physicalproperties (such as hydrophobicity) of the polypeptide of the invention.Linker sequences can be composed of flexible residues like glycine andserine. It may be preferred that the linker sequence does not adopt asecondary structure (such as a α-helical structure or a β-sheet) inorder to ensure maximal flexibility of the attached TTL recognitionmotif.

In the polypeptide of the invention, a tyrosine derivative can becovalently bonded to said recognition sequence. The tyrosine derivativemay be substituted with the above mentioned functional groups atpositions 2, 3 and 4 as well as at the benzylic position. The functionalgroups may be connected directly at the above mentioned positions or viaa spacer, such as an alkyl spacer in between. By way of example, thetyrosine derivative may be a 3-substituted or 4-substituted tyrosine,such as 3- or 4-substituted tyrosine derivative is 3-nitrotyrosine,3-aminotyrosine, 3-azidotyrosine, 3-formyltyrosine, 3-acetyltyrosine,3-iodotyrosine or 4-aminophenylalanine. Also encompassed by the term“tyrosine derivative” is phenylalanine or any other substrate that isattached by tubulin tyrosine ligase to the C-terminus of a polypeptidewhich preferably comprises a recognition sequence for TTL.Advantageously said other substrate resembles tyrosine or y tyrosinederivative as described herein. Preferably said other substrate containsan unnatural functional group for chemoselective or bioorthogonalmodifications.

The term “covalently bonded” is used herein interchangeably with theterms “covalently attached to” and “covalently joined” and refers to atype of chemical bond involving the sharing of two electron pairsbetween atoms. Without wishing to be bound by a specific theory, it isenvisaged that the tyrosine derivative is covalently attached to the TTLrecognition sequence by the action of the TTL, so that the tyrosinederivative is attached to the ultimate C-terminal amino acid of therecognition sequence, which is designated X₁ herein. The same appliesfor the attachment of tyrosine, mutatis mutandis. The resultingC-terminal amino acid sequence will then be X₄X₃X₂X₁X₀, wherein X₀refers to a tyrosine or a tyrosine derivative.

The tyrosine derivative may further contain an unnatural (non-natural)functional group, which is preferably used for chemoselective orbioorthogonal modifications. The term “click chemistry” refers to achemical philosophy introduced by Kolb, Finn and Sharpless in 2001 andencompasses a group of powerful linking reactions that are able togenerate covalent bonds quickly and reliably by joining small unitscomprising reactive groups together. Click chemistry reactions aretypically modular, wide in scope, give high chemical yields, generateinoffensive byproducts, are stereospecific, exhibit a largethermodynamic driving force >84 kJ/mol to favor a reaction with a singlereaction product, and/or can be carried using readily available startingmaterials and reagents out under simple, physiological reactionconditions. In addition, click chemistry reactions preferably use notoxic solvents or use a solvent that is benign or easily removed(preferably water), and/or provides simple product isolation bynon-chromatographic methods (crystallisation or distillation). Adistinct exothermic reaction makes a reactant “spring loaded”.

Click chemistry reactions comprise, e.g., cycloaddition reactions,especially from the 1,3-dipolar family, hetero-Diels-Alder reactions;nucleophilic ring-opening reactions, e.g. of strained heterocyclicelectrophiles, such as epoxides, aziridines, cyclic sulfates, cyclicsulfamidates, aziridinium ions and episulfonium ions; carbonyl chemistryof the non-aldol type (e.g. the formation of oxime ethers, hydrazonesand aromatic heterocycles); and addition to carbon-carbon multiplebonds; e.g. oxidation reactions, such as epoxidation dihydroxylation,aziridination, and nitrosyl and sulfenyl halide additions but alsocertain Michael addition reactions. General principles of clickchemistry reactions have been described by Kolb, Finn and Sharpless(2001). It is within the knowledge of the person skilled in the art toselect a click chemistry reaction that is suitable for attaching adesired moiety to the tyrosine derivative covalently bonded to thepolypeptide of the invention.

The term “click chemistry handle,” as used herein, refers to a reactant,or a reactive group, that can partake in a click chemistry reaction.Such a reactant or reactive group is preferably an unnatural(non-natural) functional group for a chemoselective or bioorthogonalmodification; however, it may alternatively be a natural functionalgroup for a chemoselective or bioorthogonal modification. For example, astrained alkyne, e.g., a cyclooctyne, is a click chemistry handle, sinceit can partake in a strain-promoted cycloaddition, e.g. strain-promotedazide-alkyne cycloaddition (SPARC). In general, click chemistryreactions require at least two molecules comprising click chemistryhandles that can react with each other. Such click chemistry handlepairs that are reactive with each other are sometimes referred to hereinas “partner click chemistry handles”. For example, an azide is a partnerclick chemistry handle to a cyclooctyne or any other alkyne. In thecontext of the present invention, the click chemistry handle canpreferably be selected from the group consisting of terminal alkyne,azide, strained alkyne, diene, dienophile, alkoxyamine, carbonyl,phosphine, hydrazide, thiol, tetrazine, alkene, and cyclooctyne. Othersuitable click chemistry handles are readily accessible to the personskilled in the art.

In the context of conjugation via click chemistry, the conjugation isvia a covalent bond formed by the reaction of the click chemistryhandles. In certain embodiments, the association is covalent, and theentities are said to be “conjugated” to one another. In someembodiments, a protein is post-translationally conjugated to anothermolecule, for example, a second protein, by forming a covalent bondbetween the protein and the other molecule after the protein has beentranslated, and, in some embodiments, after the protein has beenisolated. In some embodiments, the post-translational conjugation of theprotein and the second molecule, for example, the second protein, iseffected via installing a click chemistry handle on the protein, and asecond click chemistry handle, which can react to the first clickchemistry handle, on the second molecule, and carrying out a clickchemistry reaction in which the click chemistry handles react and form acovalent bond between the protein and the second molecule, thusgenerating a chimeric protein. In some embodiments, two proteins areconjugated at their respective C-termini, generating a C—C conjugatedchimeric protein. In some embodiments, two proteins are conjugated attheir respective N-termini, generating an N—N conjugated chimericprotein.

The term “alkene” refers to a hydrocarbon having at least onecarbon-carbon double bond.

The term “alkyne” refers to a hydrocarbon having at least onecarbon-carbon triple bond. As used herein, the term “terminal alkyne”refers to an alkyne wherein at least one hydrogen atom is bonded to atriply bonded carbon atom. The term “strained alkyne” refers to As usedherein the term “strained alkyne group” may comprise the ring thatcomprises a carbon to carbon triple bond and may also comprisesubstituent groups. Cyclooctyne is an exemplary strained alkyne that isenvisaged for use in the present invention, e.g. Dibenzocyclooctyne(DBCO).

The term “azide” or “azido,” as used herein, refers to a group of theformula (—N₃).

The term “diene” refers to a hydrocarbon that contains two carbon doublebonds.

The term “dienophile” refers to a compound that reacts with a diene in aDiels-Alder reaction to give a cycloaddition product.

The term “alkoxyamine” refers to any alkoxy derivative of an amine.

The term “alkoxy” refers to an alkyl group bonded through an oxygen(—O—).

The term “amine” refers to a derivative of ammonia, wherein one or morehydrogen atoms have been replaced by a substituent such as an alkyl oraryl group.

The terms “alk” or “alkyl” refer to straight or branched chainhydrocarbon groups having 1 to 12 carbon atoms, preferably 1 to 8 carbonatoms.

The term “carbonyl” refers to a group comprising a carbon atomdouble-bonded to an oxygen atom. Examples include ketones, aldehydes orcarboxylic acids or protected forms thereof.

The term “phosphine” refers to the compound with the chemical formulaPZ¹Z²Z³, where each of Z¹, Z³ and Z² is independently selected from thegroup consisting of hydrogen, substituted or unsubstituted alkyl,cycloalkyl, heterocycloalkyl, heterocyclic, aryl, substituted aryl,heteroaryl, silyl, alkoxy, aryloxy, amino and combinations thereof. Theterm “phosphonite” P(OZ¹)(OZ²)Z³, where each of Z¹, Z³ and Z² isindependently selected from the group consisting of hydrogen,substituted or unsubstituted alkyl, cycloalkyl, heterocycloalkyl,heterocyclic, aryl, substituted aryl, heteroaryl, silyl, alkoxy,aryloxy, amino and combinations thereof. The term “phosphite”P(OZ¹)(OZ²)(OZ³), where each of Z¹, Z³ and Z² is independently selectedfrom the group consisting of hydrogen, substituted or unsubstitutedalkyl, cycloalkyl, heterocycloalkyl, heterocyclic, aryl, substitutedaryl, heteroaryl, silyl, alkoxy, aryloxy, amino and combinationsthereof.

The term “hydrazide” refers to a compound having a nitrogen-nitrogencovalent bond with four substituents with at least one of them being anacyl group.

The term “thio” or “thiol,” as used herein, refers to a group of theformula (—SR), wherein R is selected from the group consisting ofhydrogen, alkyl, substituted alkyl, cycloalkyl, substituted cycloalkyl,heterocycloalkyl, substituted heterocycloalkyl, aryl, substituted aryl,heteroaryl, substituted heteroaryl, alkoxy, aryloxy, silyl andcombinations thereof. A “substituted thiol” refers to a group of theformula (—SR^(r)), wherein R^(r) can be any substituent that results inthe formation of a stable moiety (e.g., a thiol protecting group;aliphatic, alkyl, alkenyl, alkynyl, heteroaliphatic, heterocyclic, aryl,heteroaryl, acyl, sulfinyl, sulfonyl, cyano, nitro, alkylaryl,arylalkyl, and the like, each of which may or may not be furthersubstituted).

The term “aliphatic,” as used herein, includes both saturated andunsaturated, nonaromatic, straight chain (i.e., unbranched), branched,acyclic, and cyclic (i.e., carbocyclic) hydrocarbons, which areoptionally substituted with one or more functional groups. As will beappreciated by one of ordinary skill in the art, “aliphatic” is intendedherein to include, but is not limited to, alkyl, alkenyl, alkynyl,cycloalkyl, cycloalkenyl, and cycloalkynyl moieties. Thus, as usedherein, the term “alkyl” includes straight, branched and cyclic alkylgroups. An analogous convention applies to other generic terms such as“alkenyl,” “alkynyl,” and the like. Furthermore, as used herein, theterms “alkyl,” “alkenyl,” “alkynyl,” and the like encompass bothsubstituted and unsubstituted groups. In certain embodiments, as usedherein, “aliphatic” is used to indicate those aliphatic groups (cyclic,acyclic, substituted, unsubstituted, branched or unbranched) having 1-20carbon atoms (C₁₋₂o aliphatic). In certain embodiments, the aliphaticgroup has 1-10 carbon atoms (C₁₋₁₀ aliphatic). In certain embodiments,the aliphatic group has 1-6 carbon atoms (C₁₋₆ aliphatic). In certainembodiments, the aliphatic group has 1-5 carbon atoms (C₁₋₅ aliphatic).In certain embodiments, the aliphatic group has 1-4 carbon atoms (C₁₋₄aliphatic). In certain embodiments, the aliphatic group has 1-3 carbonatoms (C₁₋₃ aliphatic). In certain embodiments, the aliphatic group has1-2 carbon atoms (C₁₋₂ aliphatic). Aliphatic group substituents include,but are not limited to, any of the substituents described herein, thatresult in the formation of a stable moiety.

The term “alkyl,” as used herein, refers to saturated, straight- orbranched-chain hydrocarbon radicals derived from a hydrocarbon moietycontaining between one and twenty carbon atoms by removal of a singlehydrogen atom. In some embodiments, the alkyl group employed in theinvention contains 1-20 carbon atoms (C₁₋₂o alkyl). In anotherembodiment, the alkyl group employed contains 1-15 carbon atoms (C₁₋₁₅alkyl). In another embodiment, the alkyl group employed contains 1-10carbon atoms (C₁₋₂₀ alkyl). In another embodiment, the alkyl groupemployed contains 1-8 carbon atoms (C₁₋₈ alkyl). In another embodiment,the alkyl group employed contains 1-6 carbon atoms (C₁₋₆ alkyl). Inanother embodiment, the alkyl group employed contains 1-5 carbon atoms(C₁₋₅-alkyl). In another embodiment, the alkyl group employed contains1-4 carbon atoms (C₁₋₄ alkyl). In another embodiment, the alkyl groupemployed contains 1-3 carbon atoms (C₁₋₃ alkyl). In another embodiment,the alkyl group employed contains 1-2 carbon atoms (C₁₋₂ alkyl).Examples of alkyl radicals include, but are not limited to, methyl,ethyl, n-propyl, isopropyl, n-butyl, iso-butyl, sec-butyl, sec-pentyl,iso-pentyl, tert-butyl, n-pentyl, neopentyl, n-hexyl, sec-hexyl,n-heptyl, n-octyl, n-decyl, n-undecyl, dodecyl, and the like, which maybear one or more substituents. Alkyl group substituents include, but arenot limited to, any of the substituents described herein, that result inthe formation of a stable moiety.

The term “alkylene,” as used herein, refers to a biradical derived froman alkyl group, as defined herein, by removal of two hydrogen atoms.Alkylene groups may be cyclic or acyclic, branched or unbranched,substituted or unsubstituted. Alkylene group substituents include, butare not limited to, any of the substituents described herein, thatresult in the formation of a stable moiety.

The term “alkenyl,” as used herein, denotes a monovalent group derivedfrom a straight- or branched-chain hydrocarbon moiety having at leastone carbon-carbon double bond by the removal of a single hydrogen atom.In certain embodiments, the alkenyl group employed in the inventioncontains 2-20 carbon atoms (C₂₋₂o alkenyl). In some embodiments, thealkenyl group employed in the invention contains 2-15 carbon atoms(C₂₋₁₅ alkenyl). In another embodiment, the alkenyl group employedcontains 2-10 carbon atoms (C₂₋₁₀ alkenyl). In still other embodiments,the alkenyl group contains 2-8 carbon atoms (C₂₋₈ alkenyl). In yet otherembodiments, the alkenyl group contains 2-6 carbons (C₂₋₆ alkenyl). Inyet other embodiments, the alkenyl group contains 2-5 carbons (C₂₋₅alkenyl). In yet other embodiments, the alkenyl group contains 2-4carbons (C₂₋₄ alkenyl). In yet other embodiments, the alkenyl groupcontains 2-3 carbons (C₂₋₃ alkenyl). In yet other embodiments, thealkenyl group contains 2 carbons (C₂ alkenyl). Alkenyl groups include,for example, ethenyl, propenyl, butenyl, and the like, which may bearone or more substituents. Alkenyl group substituents include, but arenot limited to, any of the substituents described herein, that result inthe formation of a stable moiety.

The term “alkenylene,” as used herein, refers to a biradical derivedfrom an alkenyl group, as defined herein, by removal of two hydrogenatoms. Alkenylene groups may be cyclic or acyclic, branched orunbranched, substituted or unsubstituted. Alkenylene group substituentsinclude, but are not limited to, any of the substituents describedherein, that result in the formation of a stable moiety.

The term “alkynyl,” as used herein, refers to a monovalent group derivedfrom a straight- or branched-chain hydrocarbon having at least onecarbon-carbon triple bond by the removal of a single hydrogen atom. Incertain embodiments, the alkynyl group employed in the inventioncontains 2-20 carbon atoms (C₂₋₂o alkynyl). In some embodiments, thealkynyl group employed in the invention contains 2-15 carbon atoms (C₂₁₅alkynyl). In another embodiment, the alkynyl group employed contains2-10 carbon atoms (C₂₋₁₀ alkynyl). In still other embodiments, thealkynyl group contains 2-8 carbon atoms (C₂₋₈ alkynyl). In still otherembodiments, the alkynyl group contains 2-6 carbon atoms (C₂₋₆ alkynyl).In still other embodiments, the alkynyl group contains 2-5 carbon atoms(C₂₋₅ alkynyl). In still other embodiments, the alkynyl group contains2-4 carbon atoms (C₂₋₄ alkynyl). In still other embodiments, the alkynylgroup contains 2-3 carbon atoms (C₂₋₃ alkynyl). In still otherembodiments, the alkynyl group contains 2 carbon atoms (C₂ alkynyl).Representative alkynyl groups include, but are not limited to, ethynyl,2-propynyl (propargyl), 1-propynyl, and the like, which may bear one ormore substituents. Alkynyl group substituents include, but are notlimited to, any of the substituents described herein, that result in theformation of a stable moiety.

The term “alkynylene,” as used herein, refers to a biradical derivedfrom an alkynylene group, as defined herein, by removal of two hydrogenatoms. Alkynylene groups may be cyclic or acyclic, branched orunbranched, substituted or unsubstituted. Alkynylene group substituentsinclude, but are not limited to, any of the substituents describedherein, that result in the formation of a stable moiety.

The term “carbocyclic” or “carbocyclyl” as used herein, refers to an asused herein, refers to a cyclic aliphatic group containing 3-10 carbonring atoms (C₃₋₁₀ carbocyclic). Carbocyclic group substituents include,but are not limited to, any of the substituents described herein, thatresult in the formation of a stable moiety.

The term “heteroaliphatic,” as used herein, refers to an aliphaticmoiety, as defined herein, which includes both saturated andunsaturated, nonaromatic, straight chain (i.e., unbranched), branched,acyclic, cyclic (i.e., heterocyclic), or polycyclic hydrocarbons, whichare optionally substituted with one or more functional groups, and thatfurther contains one or more heteroatoms (e.g., oxygen, sulfur,nitrogen, phosphorus, or silicon atoms) between carbon atoms. In certainembodiments, heteroaliphatic moieties are substituted by independentreplacement of one or more of the hydrogen atoms thereon with one ormore substituents. As will be appreciated by one of ordinary skill inthe art, “heteroaliphatic” is intended herein to include, but is notlimited to, heteroalkyl, heteroalkenyl, heteroalkynyl, heterocycloalkyl,heterocycloalkenyl, and heterocycloalkynyl moieties. Thus, the term“heteroaliphatic” includes the terms “heteroalkyl,” “heteroalkenyl,”“heteroalkynyl,” and the like. Furthermore, as used herein, the terms“heteroalkyl,” “heteroalkenyl,” “heteroalkynyl,” and the like encompassboth substituted and unsubstituted groups. In certain embodiments, asused herein, “heteroaliphatic” is used to indicate those heteroaliphaticgroups (cyclic, acyclic, substituted, unsubstituted, branched orunbranched) having 1-20 carbon atoms and 1-6 heteroatoms (C₁₋₂oheteroaliphatic). In certain embodiments, the heteroaliphatic groupcontains 1-10 carbon atoms and 1-4 heteroatoms (C₁₋₁₀ heteroaliphatic).In certain embodiments, the heteroaliphatic group contains 1-6 carbonatoms and 1-3 heteroatoms (C₁₋₆ heteroaliphatic). In certainembodiments, the heteroaliphatic group contains 1-5 carbon atoms and 1-3heteroatoms (C₁₋₅ heteroaliphatic). In certain embodiments, theheteroaliphatic group contains 1-4 carbon atoms and 1-2 heteroatoms(C₁₋₄ heteroaliphatic). In certain embodiments, the heteroaliphaticgroup contains 1-3 carbon atoms and 1 heteroatom (C₁₋₃ heteroaliphatic).In certain embodiments, the heteroaliphatic group contains 1-2 carbonatoms and 1 heteroatom (C₁₋₂ heteroaliphatic). Heteroaliphatic groupsubstituents include, but are not limited to, any of the substituentsdescribed herein, that result in the formation of a stable moiety.

The term “heteroalkyl,” as used herein, refers to an alkyl moiety, asdefined herein, which contain one or more heteroatoms (e.g., oxygen,sulfur, nitrogen, phosphorus, or silicon atoms) in between carbon atoms.In certain embodiments, the heteroalkyl group contains 1-20 carbon atomsand 1-6 heteroatoms (C₁₋₂o heteroalkyl). In certain embodiments, theheteroalkyl group contains 1-10 carbon atoms and 1-4 heteroatoms (C₁₋₁₀heteroalkyl). In certain embodiments, the heteroalkyl group contains 1-6carbon atoms and 1-3 heteroatoms (C₁₋₆ heteroalkyl). In certainembodiments, the heteroalkyl group contains 1-5 carbon atoms and 1-3heteroatoms (C₁₋₅ heteroalkyl). In certain embodiments, the heteroalkylgroup contains 1-4 carbon atoms and 1-2 heteroatoms (C₁₋₄ heteroalkyl).In certain embodiments, the heteroalkyl group contains 1-3 carbon atomsand 1 heteroatom (C₁₋₃ heteroalkyl). In certain embodiments, theheteroalkyl group contains 1-2 carbon atoms and 1 heteroatom (C₁₋₂heteroalkyl). The term “heteroalkylene,” as used herein, refers to abiradical derived from an heteroalkyl group, as defined herein, byremoval of two hydrogen atoms. Heteroalkylene groups may be cyclic oracyclic, branched or unbranched, substituted or unsubstituted.

Heteroalkylene group substituents include, but are not limited to, anyof the substituents described herein, that result in the formation of astable moiety.

The term “heteroalkenyl,” as used herein, refers to an alkenyl moiety,as defined herein, which further contains one or more heteroatoms (e.g.,oxygen, sulfur, nitrogen, phosphorus, or silicon atoms) in betweencarbon atoms. In certain embodiments, the heteroalkenyl group contains2-20 carbon atoms and 1-6 heteroatoms (C₂₋₂₀ heteroalkenyl). In certainembodiments, the heteroalkenyl group contains 2-10 carbon atoms and 1-4heteroatoms (C₂₋₁₀ heteroalkenyl). In certain embodiments, theheteroalkenyl group contains 2-6 carbon atoms and 1-3 heteroatoms (02-6heteroalkenyl). In certain embodiments, the heteroalkenyl group contains2-5 carbon atoms and 1-3 heteroatoms (C2-5 heteroalkenyl). In certainembodiments, the heteroalkenyl group contains 2-4 carbon atoms and 1-2heteroatoms (C2-4 heteroalkenyl). In certain embodiments, theheteroalkenyl group contains 2-3 carbon atoms and 1 heteroatom (C₂₋₃heteroalkenyl). The term “heteroalkenylene,” as used herein, refers to abiradical derived from an heteroalkenyl group, as defined herein, byremoval of two hydrogen atoms. Heteroalkenylene groups may be cyclic oracyclic, branched or unbranched, substituted or unsubstituted.

The term “heteroalkynyl,” as used herein, refers to an alkynyl moiety,as defined herein, which further contains one or more heteroatoms (e.g.,oxygen, sulfur, nitrogen, phosphorus, or silicon atoms) in betweencarbon atoms. In certain embodiments, the heteroalkynyl group contains2-20 carbon atoms and 1-6 heteroatoms (C₂₋₂₀ heteroalkynyl).

In certain embodiments, the heteroalkynyl group contains 2-10 carbonatoms and 1-4 heteroatoms (C₂₋₁₀ heteroalkynyl). In certain embodiments,the heteroalkynyl group contains 2-6 carbon atoms and 1-3 heteroatoms(C₂₋₆ heteroalkynyl). In certain embodiments, the heteroalkynyl groupcontains 2-5 carbon atoms and 1-3 heteroatoms (C₂₋₅ heteroalkynyl). Incertain embodiments, the heteroalkynyl group contains 2-4 carbon atomsand 1-2 heteroatoms (C₂₋₄ heteroalkynyl). In certain embodiments, theheteroalkynyl group contains 2-3 carbon atoms and 1 heteroatom (C₂₋₃heteroalkynyl). The term “heteroalkynylene,” as used herein, refers to abiradical derived from an heteroalkynyl group, as defined herein, byremoval of two hydrogen atoms. Heteroalkynylene groups may be cyclic oracyclic, branched or unbranched, substituted or unsubstituted.

The term “heterocyclic,” “heterocycles,” or “heterocyclyl,” as usedherein, refers to a cyclic heteroaliphatic group. A heterocyclic grouprefers to a non-aromatic, partially unsaturated or fully saturated, 3-to 10-membered ring system, which includes single rings of 3 to 8 atomsin size, and bi- and tri-cyclic ring systems which may include aromaticfive- or six-membered aryl or heteroaryl groups fused to a non-aromaticring. These heterocyclic rings include those having from one to threeheteroatoms independently selected from oxygen, sulfur, and nitrogen, inwhich the nitrogen and sulfur heteroatoms may optionally be oxidized andthe nitrogen heteroatom may optionally be quaternized. In certainembodiments, the term heterocyclic refers to a non-aromatic 5-, 6-, or7-membered ring or polycyclic group wherein at least one ring atom is aheteroatom selected from O, S, and N (wherein the nitrogen and sulfurheteroatoms may be optionally oxidized), and the remaining ring atomsare carbon, the radical being joined to the rest of the molecule via anyof the ring atoms. Heterocycyl groups include, but are not limited to, abi- or tri-cyclic group, comprising fused five, six, or seven-memberedrings having between one and three heteroatoms independently selectedfrom the oxygen, sulfur, and nitrogen, wherein (i) each 5-membered ringhas 0 to 2 double bonds, each 6-membered ring has 0 to 2 double bonds,and each 7-membered ring has 0 to 3 double bonds, (ii) the nitrogen andsulfur heteroatoms may be optionally oxidized, (iii) the nitrogenheteroatom may optionally be quaternized, and (iv) any of the aboveheterocyclic rings may be fused to an aryl or heteroaryl ring.

Exemplary heterocycles include azacyclopropanyl, azacyclobutanyl,1,3-diazatidinyl, piperidinyl, piperazinyl, azocanyl, thiaranyl,thietanyl, tetrahydrothiophenyl, dithiolanyl, thiacyclohexanyl,oxiranyl, oxetanyl, tetrahydrofuranyl, tetrahydropuranyl, dioxanyl,oxathiolanyl, morpholinyl, thioxanyl, tetrahydronaphthyl, and the like,which may bear one or more substituents. Substituents include, but arenot limited to, any of the substituents described herein, that result inthe formation of a stable moiety.

The term “aryl,” as used herein, refers to an aromatic mono- orpolycyclic ring system having 3-20 ring atoms, of which all the ringatoms are carbon, and which may be substituted or unsubstituted. Incertain embodiments of the present invention, “aryl” refers to a mono,bi, or tricyclic C4-C20 aromatic ring system having one, two, or threearomatic rings which include, but are not limited to, phenyl, biphenyl,naphthyl, and the like, which may bear one or more substituents. Arylsubstituents include, but are not limited to, any of the substituentsdescribed herein, that result in the formation of a stable moiety. Theterm “arylene,” as used herein refers to an aryl biradical derived froman aryl group, as defined herein, by removal of two hydrogen atoms.Arylene groups may be substituted or unsubstituted. Arylene groupsubstituents include, but are not limited to, any of the substituentsdescribed herein, that result in the formation of a stable moiety.Additionally, arylene groups may be incorporated as a linker group intoan alkylene, alkenylene, alkynylene, heteroalkylene, heteroalkenylene,or heteroalkynylene group, as defined herein.

The term “heteroaryl,” as used herein, refers to an aromatic mono- orpolycyclic ring system having 3-20 ring atoms, of which one ring atom isselected from S, O, and N; zero, one, or two ring atoms are additionalheteroatoms independently selected from S, O, and N; and the remainingring atoms are carbon, the radical being joined to the rest of themolecule via any of the ring atoms. Exemplary heteroaryls include, butare not limited to pyrrolyl, pyrazolyl, imidazolyl, pyridinyl,pyrimidinyl, pyrazinyl, pyridazinyl, triazinyl, tetrazinyl,pyyrolizinyl, indolyl, quinolinyl, isoquinolinyl, benzoimidazolyl,indazolyl, quinolinyl, isoquinolinyl, quinolizinyl, cinnolinyl,quinazolynyl, phthalazinyl, naphthridinyl, quinoxalinyl, thiophenyl,thianaphthenyl, furanyl, benzofuranyl, benzothiazolyl, thiazolynyl,isothiazolyl, thiadiazolynyl, oxazolyl, isoxazolyl, oxadiaziolyl,oxadiaziolyl, and the like, which may bear one or more substituents.Heteroaryl substituents include, but are not limited to, any of thesubstituents described herein, that result in the formation of a stablemoiety.

The term “heteroarylene,” as used herein, refers to a biradical derivedfrom an heteroaryl group, as defined herein, by removal of two hydrogenatoms. Heteroarylene groups may be substituted or unsubstituted.Additionally, heteroarylene groups may be incorporated as a linker groupinto an alkylene, alkenylene, alkynylene, heteroalkylene,heteroalkenylene, or heteroalkynylene group, as defined herein.Heteroarylene group substituents include, but are not limited to, any ofthe substituents described herein, that result in the formation of astable moiety.

The term “acyl,” as used herein, is a subset of a substituted alkylgroup, and refers to a group having the general formula —C(═O)R^(A),—C(═O)OR^(A), —C(═O)—O—C(═O)R^(A), —C(═O)SR^(A), —C(═O)N(R^(A))₂,—C(═S)R^(A), —C(═S)N(R^(A))₂, and —C(═S)S(R^(A)), —C(═NR^(A))R^(A),—C(═NR^(A))OR^(A), —C(═NR^(A))SR^(A), and —C(═NR^(A))N(R^(A))₂, whereinR^(A) is hydrogen; halogen; substituted or unsubstituted hydroxyl;substituted or unsubstituted thiol; substituted or unsubstituted amino;acyl; optionally substituted aliphatic; optionally substitutedheteroaliphatic; optionally substituted alkyl; optionally substitutedalkenyl; optionally substituted alkynyl; optionally substituted aryl,optionally substituted heteroaryl, aliphaticoxy, heteroaliphaticoxy,alkyloxy, heteroalkyloxy, aryloxy, heteroaryloxy, aliphaticthioxy,heteroaliphaticthioxy, alkylthioxy, heteroalkylthioxy, arylthioxy,heteroarylthioxy, mono- or di-aliphaticamino, mono- ordi-heteroaliphaticamino, mono- or di-alkylamino, mono- ordi-heteroalkylamino, mono- or di-arylamino, or mono- ordi-heteroarylamino; or two R^(A) groups taken together form a 5- to6-membered heterocyclic ring. Exemplary acyl groups include aldehydes(—CHO), carboxylic acids (—CO₂H), ketones, acyl halides, esters, amides,imines, carbonates, carbamates, and ureas. Acyl substituents include,but are not limited to, any of the substituents described herein, thatresult in the formation of a stable moiety.

The term “acylene,” as used herein, is a subset of a substitutedalkylene, substituted alkenylene, substituted alkynylene, substitutedheteroalkylene, substituted heteroalkenylene, or substitutedheteroalkynylene group, and refers to an acyl group having the generalformulae: —R^(o)—(C═X¹)—R⁰—, —R^(o)—X²(C═X¹)—R⁰—, or—R^(o)—X²(C═X¹)X³—R⁰—, where X¹, X², X³ is, independently, oxygen,sulfur, or NR^(r), wherein R^(r) is hydrogen or optionally substitutedaliphatic, and R⁰ is an optionally substituted alkylene, alkenylene,alkynylene, heteroalkylene, heteroalkenylene, or heteroalkynylene group,as defined herein. Exemplary acylene groups wherein R^(o) is alkyleneincludes —(CH₂)_(T)—O(C═O)—(CH₂)_(T); —(CH₂)_(T)—NR^(r)(C═O)—(CH₂)_(T)—;—(CH₂)_(T)—O(C═NR^(r))—(CH₂)_(T)—;—(CH₂)_(T)—NR^(r)(C═NR^(r))—(CH₂)_(T)—; —(CH₂)_(T)(C═O)—(CH₂)^; _(CH₂)^(C═NR^(R))—(CH₂)^; —(CH₂)_(T)—S(C═S)—(CH₂)_(T); —(CH₂)_(T)NR^(r)(C═S)—(CH₂)_(T); —(CH₂)_(T)—S(C═NR^(r))—(CH₂)_(T);—(CH₂)_(T)—O(C═S)—(CH₂)_(T); —(CH₂)_(T)—(C═S)—(CH₂)_(T)—; or—(CH₂)_(T)—S(C═O)—(CH₂)_(T), and the like, which may bear one or moresubstituents; and wherein each instance of T is, independently, aninteger between 0 to 20. Acylene substituents include, but are notlimited to, any of the substituents described herein, that result in theformation of a stable moiety.

It should be noted that the invention is not limited to the foregoing,exemplary click chemistry handles, and additional click chemistryhandles, reactive click chemistry handle pairs, and reaction conditionsfor such click chemistry handle pairs will be apparent to those of skillin the art.

Other methods suitable for conjugating a moiety to the tyrosinederivative of the polypeptide of the invention comprise Staudingerreactions (e.g. Staudinger-ligation, Staudinger-Phosphite reaction),strain-promoted cycloadditions, tetrazine ligations, inverse-electrondemand Diels-Alder reactions, thiazolidine-forming reactions ofaldehydes or ketones with 1,2-aminothiols, oxazolidine-forming reactionsof aldehydes or ketones with 1,2-aminoalcohols, acetal-forming reactionsof aldehydes or ketones with 1,2-diols, metal-catalyzed, in particularPd-, Cu, Ni and Fe-catalyzed cross couplings with tyrosine-derivativessubstituted with electron-withdrawing groups.

It is envisaged that a moiety can be attached to the tyrosine derivativecovalently bonded to the polypeptide of the invention, for example, byclick chemistry or any other suitable method as described herein. Amoiety may thus be conjugated to the tyrosine derivative of atyrosinated polypeptide by a non-peptidic bond, however, in thealternative it may also be conjugated to the tyrosine derivative of atyrosinated polypeptide by a peptidic-bond. Said moiety can be acarrier, a polypeptide, a detectable label, a chemical compound, anucleic acid, a carbohydrate, or a lipid.

The term “carrier” when used herein refers to a moiety, such as, e.g., amolecule or polymer, which acts to improve delivery, effectivenessand/or stability of the polypeptide of the invention. For example, ifthe polypeptide of the invention is envisaged for treatment of a subjectas described herein, the carrier may be a pharmaceutically acceptablecarrier that can direct the polypeptide of the invention to a specificlocation, facilitate its transport, enhance its serum stability,bioavailability, and the like. Pharmaceutically acceptable carriers aredescribed herein. A carrier may, however, also be a bead, such as amagnetic bead, or a solid surface. A solid surface may be selected frompolystyrene, polypropylene, polyvinylchloride, polyacrylamide,celluloses, dextrans, synthetic polymers and co-polymers, latex, silica,agarose, metal, glass, or carbon.

Alternatively, the moiety that is conjugated to the tyrosine derivativeattached to the polypeptide of the invention is a polypeptide(hereinafter referred to as “polypeptide moiety”). Any polypeptide isconceivable that can be attached to the tyrosine derivative covalentlybonded to the polypeptide of the invention. The polypeptide moiety mayrequire modification in order to be able to be attached.

In one particular embodiment, the polypeptide moiety is an antibody orfragment thereof. As is well known in the art, an antibody is animmunoglobulin molecule capable of specific binding to a target, such asa carbohydrate, polynucleotide, lipid, polypeptide, etc., through atleast one epitope recognition site, located in the variable region ofthe immunoglobulin molecule. As used herein, the term encompassesmonoclonal antibodies, chimeric antibodies, humanized antibodies, humanantibodies, scFv, DART, domain antibodies, nanobodies, adnectin,affibodies, anticalins, DARPins, aptamers or functional equivalentsthereof of any one of the aforementioned antibody species as well asaffinity binders.

A “detectable label” is a molecule or material that can produce adetectable (such as visually, electronically or otherwise) signal thatindicates the presence and/or concentration of the label in a sample.Thereby, e.g., the presence, location and/or concentration of thepolypeptide in a sample can be detected by detecting the signal producedby the detectable label. A detectable label can be detected directly orindirectly, It will be appreciated that the label may be attached to orincorporated into a molecule, for example, a protein, polypeptide, orother entity, at any position. It will be appreciated that, in certainembodiments, a label may react with a suitable substrate (e.g., aluciferin) to generate a detectable signal. In particular, thedetectable label can be a fluorophore, an enzyme (peroxidase,luciferase), a radioisotope, a fluorescent protein, or a fluorescentdye. Other dectectable labels include chemiluminescent labels,electrochemiluminescent labels, bioluminescent labels, polymers, polymerparticles, metal particles, haptens, and dyes.

A “fluorophore” (or fluorochrome) is a fluorescent chemical compoundthat can re-emit light upon light excitation. Examples of fluorophoresinclude 5-(and 6)-carboxyfluorescein, 5- or 6-carboxyfluorescein,6-(fluorescein)-5-(and 6)-carboxamido hexanoic acid, fluoresceinisothiocyanate, rhodamine, tetramethylrhodamine, and dyes such as Cy2,Cy3, and Cy5, optionally substituted coumarin including AMCA, PerCP,phycobiliproteins including R-phycoerythrin (RPE) and allophycoerythrin(APC), Texas Red, Princeton Red, inorganic fluorescent labels such asparticles based on semiconductor material like coated CdSenanocrystallites.

Examples for fluorescent proteins include Exemplary fluorescent proteinsinclude, e.g., Sirius, Azurite, EBFP, EBFP2, TagBFP, mTurquoise, ECFP,Cerulean, CyPet, TagCFP, mTFPI, mUkGI, mAGI, AcGFPI, TagGFP2, EGFP, GFP,mWasabi, EmGFP, YFP, TagYPF, Ypet, EYFP, Topaz, SYFP2, Venus, Citrine,mKO, mK02, mOrange, mOrange2, TagRFP, TagRFP-T, mStrawberry, mRuby,mCherry, mRaspberry, mKate2, mPlum, mNeptune, mKalama2, T-Sapphire,mAmetrine, mKeima, UnaG, dsRed, eqFP611, Dronpa, KFP, EosFP, Dendra, andIrisFP.

Examples of enzymes used as enzymatic labels include horseradishperoxidase (HRP), alkaline phosphatase (ALP or AP), β-galactosidase(GAL), glucose-6-phosphate dehydrogenase, β-N-acetylglucosamimidase,β-glucuronidase, invertase, Xanthine Oxidase, firefly luciferase andglucose oxidase (GO).

Examples of radioactive labels include radioactive isotopes of hydrogen,iodide, cobalt, selenium, tritium, carbon, sulfur and phosphorous. ²H,³H, ¹³C, ¹⁴C, ¹⁵N, ¹⁸F, ³¹P, ³²P, ³⁵S, ⁶⁷Ga, ⁷⁶Br, ^(99m)Tc (Tc-99m),^(m)In, ¹²³I, ¹²⁵I, ¹³¹I, ¹⁵³Gd, ¹⁶⁹Yb, and ¹⁸⁶Re.

A “chemical compound” can in general be any chemical compound that canbe covalently linked to the tyrosine derivative attached to thepolypeptide of the invention. In particular, the chemical compound canbe a small molecule, a polymer, such as a synthetic polymer (PEG) or atherapeutic agent, such as a cytotoxic agent. As such, for example anantibody can be equipped by the means and methods of the presentinvention with a cytotoxic drug to become an antibody-drug conjugate(ADC). Of course, it is envisaged that a linker is conjugated to atyrosine derivative and a cytotoxic drug, if necessary. However, thecytotoxic drug may also be conjugated to the tyrosine derivative withouta linker. Examples of cytotoxic drugs are doxorubicin or derivativesthereof, maytanosinoids, e.g. DM1 or DM4, auristatins, e.g. auristatin Eor auristatin F, calicheamicins, CC-1065, duocarmycins, anthracyclines,pyrrolobentodiazepins, centanamycin, iriontecan metabolite (SN38).

Exemplary small molecules include hormones, nucleotides, amino acids,sugars, lipids and organic compounds having a molecular weight of lessthan 100 kD. In some embodiments, small molecules that are approved bythe FDA can be preferred.

Exemplary polymers include peptides, oligonucleotides, and polymericorganic compounds. In particular, suitable polymers include, e.g.,elastin-like polypeptides (ELP), polypeptide chains of varying length(e.g., XTEN® technology or PASylation®), and carbohydrates, such ashydroxyethyl starch (e.g., HESylation®), polysialic acid (e.g., PolyXen®technology) or polyethylene glycol (PEGylation®).

The term “nucleic acid” as used herein refers to a polymer ofnucleotides linked together by phosphodiester bonds. The term in generalincludes any polynucleotide in any possible configuration, such assingle stranded, double stranded, linear, circular or a combinationthereof. Nucleic acids include, e.g., DNA molecules, RNA molecules,analogues of the DNA or RNA generated using nucleotide analogues, andaptamers. An aptamer is typically a nucleic acid molecule that is ableto bind molecules such as peptides, proteins and low molecular weightcompounds.

The invention additionally provides a pharmaceutical compositioncomprising the polypeptide of the invention. A pharmaceuticalcomposition according to the present invention may further comprise oneor more pharmaceutically acceptable carriers. In a specific embodiment,the term “pharmaceutically acceptable” means approved by a regulatoryagency or other generally recognized pharmacopoeia for use in animals,and more particularly in humans. Pharmaceutically acceptable carriersare well known in the art and include, for example, aqueous solutionssuch as water, 5% dextrose, or physiologically buffered saline or othersolvents or vehicles such as glycols, glycerol, oils such as olive oil,or injectable organic esters that are suitable for administration to ahuman or non-human subject. Particular exemplary pharmaceuticallyacceptable carriers include (biodegradable) liposomes; microspheres madeof the biodegradable polymer poly(D,L-lactic-coglycolic acid (PLGA),albumin microspheres; synthetic polymers (soluble); nanofibers,protein-DNA complexes; protein conjugates; erythrocytes; or virosomes.Various carrier based dosage forms comprise solid lipid nanoparticles(SLNs), polymeric nanoparticles, ceramic nanoparticles, hydrogelnanoparticles, copolymerized peptide nanoparticles, nanocrystals andnanosuspensions, nanocrystals, nanotubes and nanowires, functionalizednanocarriers, nanospheres, nanocapsules, liposomes, lipid emulsions,lipid microtubules/microcylinders, lipid microbubbles, lipospheres,lipopolyplexes, inverse lipid micelles, dendrimers, ethosomes,multicomposite ultrathin capsules, aquasomes, pharmacosomes,colloidosomes, niosomes, discomes, proniosomes, microspheres,microemulsions and polymeric micelles. Other suitable pharmaceuticallyacceptable carriers and excipients are inter alia described inRemington's Pharmaceutical Sciences, 15^(th) Ed., Mack Publishing Co.,New Jersey (1991) and Bauer et al., Pharmazeutische Technologie, 5^(th)Ed., Govi-Verlag Frankfurt (1997). See, e.g., Remington: The Science andPractice of Pharmacy, 21^(st) edition; Lippincott Williams & Wilkins,2005.

In some embodiments, a pharmaceutically acceptable carrier orcomposition is sterile. A pharmaceutical composition can comprise, inaddition to the active agent, physiologically acceptable compounds thatact, for example, as bulking agents, fillers, solubilizers, stabilizers,osmotic agents, uptake enhancers, etc. Physiologically acceptablecompounds include, for example, carbohydrates, such as glucose, sucrose,lactose; dextrans; polyols such as mannitol; antioxidants, such asascorbic acid or glutathione; preservatives; chelating agents; buffers;or other stabilizers or excipients.

The choice of a pharmaceutically acceptable carrier(s) and/orphysiologically acceptable compound(s) can depend for example, on thenature of the active agent, e.g., solubility, compatibility (meaningthat the substances can be present together in the composition withoutinteracting in a manner that would substantially reduce thepharmaceutical efficacy of the pharmaceutical composition under ordinaryuse situations) and/or route of administration of the composition.

Pharmaceutical compositions of the invention comprise a therapeuticallyeffective amount of the polypeptide of the invention and can beformulated in various forms, e.g. in solid, liquid, gaseous orlyophilized form and may be, inter alia, in the form of an ointment, acream, transdermal patches, a gel, powder, a tablet, solution, anaerosol, granules, pills, suspensions, emulsions, capsules, syrups,liquids, elixirs, extracts, tincture or fluid extracts or in a formwhich is particularly suitable for topical or oral administration. Avariety of routes are applicable for administration of the polypeptideof the invention, including, but not limited to, orally, topically,transdermally, subcutaneously, intravenously, intraperitoneally,intramuscularly or intraocularly. However, any other route may readilybe chosen by the person skilled in the art if desired.

The pharmaceutical compositions can be used for the treatment of a widevariety of different diseases and disorders. Thus the invention alsoenvisages methods of treatment comprising administering an inventivepolypeptide to a subject in need thereof. The subject is typically amammal, e.g., a human. In some embodiments the subject is a non-humananimal that serves as a model for a disease or disorder that affectshumans. The animal model may be used, e.g., in preclinical studies,e.g., to assess efficacy and/or determine a suitable dose. In someembodiments, an inventive protein is administered prophylactically,e.g., to a subject who does not exhibit signs or symptoms of the diseaseor disorder (but may be at increased risk of developing the disorder oris expected to develop the disease or disorder). In some embodiments aninventive protein is administered to a subject who has developed one ormore signs or symptoms of the disease or disorder, e.g., the subject hasbeen diagnose as having the disease or disorder. Optionally, the methodcomprises diagnosing the subject as having a disease or disorder forwhich the protein is an appropriate treatment. By “therapeuticallyeffective amount” is meant an amount of the polypeptide of the inventionthat elicits a desired therapeutic effect. The exact amount dose willdepend on the purpose of the treatment, and will be ascertainable by oneskilled in the art using known techniques. As is known in the art anddescribed above, adjustments for age, body weight, general health, sex,diet, drug interaction and the severity of the condition may benecessary, and will be ascertainable with routine experimentation bythose skilled in the art.

The pharmaceutical composition of the present invention may furthercomprise one or more additional therapeutic agents. Preferably, saidagents are therapeutically effective for treatment of the respectivedisease.

Further, the invention relates to a diagnostic composition comprisingthe polypeptide of the invention. The diagnostic composition maycomprise means for diagnosis, such as detection agents.

Also, a kit comprising means for performing the methods described hereinis provided. The kit may comprise an expression vector which allowsexpression of a protein of interest fused at its C-Terminus to arecognition sequence for tubulin tyrosine ligase having, a tubulintyrosine ligase and a tyrosine derivative and/or a buffer solution asdescribed herein which can be used for the tyronisnation.

The term “expression vector” refers to a carrier nucleic acid moleculewhich has the ability to incorporate and transcribe heterologous nucleicacid sequences in a host, host cell or in vitro. Selection ofappropriate expression or transcription vectors is within the knowledgeof those skilled in the art. Many prokaryotic and eukaryotic expressionvectors are commercially available. Examples of vectors used in thepresent invention include plasmids, viruses, phagemids, bacteriophages,retroviruses, cosmids or F-factors. Specific vectors may be used forspecific host or host cell types. Numerous examples of vectors are knownin the art and are commercially available (Sambrook and Russell,Molecular Cloning: A Laboratory Manual, 3rd edition (Jan. 15, 2001) ColdSpring Harbor Laboratory Press, ISBN: 0879695765). Examples of vectorscommonly used with bacteria include the pET series (Novagen), pGEXseries (Ge Healthcare), pBAD-series (Invitrogen). Examples of vectors inyeasts are the pPic series for Pichia (Invitrogen), the pKlac systemfrom Kluyveromyces lactis (New England biolabs), S. cereviseae vectors(Patel et al. Biotechnol Lett. 2003 25(4):331-334) and the pYes systemfor S. cereviseae (Invitrogen). Examples of vectors for use in fungi arethe pBAR series (described in Pall et al. 1993. Fungal GeneticsNewsletter 40: 59-61). The pIEx plasmid based system (Merck) or thebaculovirus based system (Merck) are two examples of systems useful forinsect cells. Examples of vectors for use in insect cells include thetetracycline regulated systems pTet and pTre, the adenovirus-basedsystem Adeno-X, the retrovirus-based system Retro-X (Clontech) and thepcDNA vectors (Invitrogen). The expression vector may benaturally-occurring or artificial, linear or circular. The vector mayalso contain an intron.

The present invention also provides a method for the production of apolypeptide comprising

(a) introducing or adding at the C-terminus of a polypeptide arecognition sequence for tubulin tyrosine ligase;

(b) optionally contacting the polypeptide obtained in step (a) in thepresence of tubulin tyrosine ligase and a tyrosine derivative underconditions suitable for the tubulin tyrosine ligase to tyrosinate saidpolypeptide with said tyrosine derivative; and

(c) optionally conjugating a moiety to said tyrosinated polypeptideobtained in step (b).

Step (c) of said method may also be seen as a preferred method step.Accordingly, said method of the present invention further comprisespreferably step (c) conjugating a moiety to said tyrosinated polypeptideobtained in step (b).

The present invention, as an alternative to the afore described method,provides a method for the production of a polypeptide, comprising

(a′) introducing or adding at the C-terminus of a polypeptide arecognition sequence for tubulin tyrosine ligase; and

(b′) contacting the polypeptide obtained in step (a′) in the presence oftubulin tyrosine ligase and a tyrosine derivative conjugated to a moietyunder conditions suitable for the tubulin tyrosine ligase to tyrosinatesaid polypeptide with said tyrosine derivative conjugated to saidmoiety.

The introduction or addition of a recognition sequence for TTL at theC-terminus of a polypeptide is done as described herein. For example,such a recognition sequence may be introduced or added by geneticengineering or by synthesis, either chemical protein synthesis or viasynthetic biology.

Several factors may affect the rate at which enzymatic reactionsproceed: temperature, pH, enzyme concentration, substrate concentration,and the presence of any inhibitors or activators. In some embodiments,it is envisaged that a buffer containing a nucleoside triphosphate, suchas ATP, potassium chloride, magnesium chloride, and a reducing agentsuch as DTT is employed in the method of the invention in order toprovide suitable conditions suitable for the TTL to tyrosinate thepolypeptide of the invention. Other exemplary conditions are describedin Ruediger et al. (1994), loc. cit.

It is envisaged herein that the pH value in the method of the inventionin order to provide suitable conditions for the TTL to tyrosinate thepolypeptide of the invention is in the range of 5 to 9, preferably 5.5to 8.5, even more preferably 6 to 8.

Furthermore, it is envisaged herein that the tyrosine derivativeconcentration in the method of the invention in order to providesuitable conditions for the TTL to tyrosinate the polypeptide of theinvention may be in the range of 0.1 mM to 10 mM, preferably 0.25 mM to5 mM, more preferably 0.5 mM to 3 mM, and even more preferably 1 mM to 2mM.

It is also envisaged herein that the reaction temperature in the methodof the invention in order to provide suitable conditions for the TTL totyrosinate the polypeptide of the invention may be in the range of 1° C.to 70° C., preferably 5° C. to 65° C., more preferably 10° C. to 60° C.,even more preferably 15° C. to 55° C., most preferably 19° C. to 43° C.,and for example 19° C. to 37° C.

A suitable reaction time for the TTL to tyrosinate the polypeptide ofthe invention may be in the range of 5 minute to 4 hours, preferably 10minutes to 3 hours, more preferably 1 hour to 3 hours.

The conjugation of a moiety to the tyrosine derivative of a tyrosinatedpolypeptide is done as described herein.

Also provided by the present invention is the use of tubulin tyrosineligase for tyrosinating a polypeptide other than tubulin having at itsC-terminus a recognition sequence for tubulin tyrosine ligase.

A method for installing a chemistry handle to the C-terminus of apolypeptide other than tubulin is also provided herein, said methodcomprising:

(a) providing a polypeptide having at its C-terminus a tubulin tyrosineligase recognition sequence; and

(b) contacting the polypeptide of step (a) in the presence of tubulintyrosine ligase and a tyrosine derivative containing an unnaturalfunctional group for chemoselective or bioorthogonal modifications underconditions suitable for the tubulin tyrosine ligase to tyrosinate saidpolypeptide with said tyrosine derivative.Said method may optionally further comprise the step of conjugating amoiety as described herein to said tyrosinated polypeptide obtained instep (b).

The present invention also provides the use of tubulin tyrosine ligasefor installing a chemistry handle to the C-terminus of a polypeptideother than tubulin, said polypeptide having at its C-terminus a tubulintyrosine ligase recognition sequence.

The embodiments and definitions of terms described in the context of themeans such as polypeptides of the invention are equally applicable tothe methods and uses described above, mutatis mutandis.

EXAMPLES Example 1: General Information

Analytical HPLC was conducted on a SHIMADZU HPLC system (Shimadzu Corp.,Kyoto, Japan) with a SIL-20A autosampler, 2 pumps LC2 AAT, a 2489UV/Visible detector, a CTO-20A column oven and an RF-10 A X2fluorescence detector using an Agilent Eclipse C18 5 μm, 250×4.6 mmRP-HPLC-column with a flow rate of 0.5 mL/min. The following gradientwas used: Method A: (A=H₂O+0.1% TFA, B=MeCN+0.1% TFA) 35% B, 0-15 min,10-100% B 15-17 min, 100% B 17-22 min, 100-35% B 22-25 min and 35% B25-30 min. UV chromatograms were recorded at 220 nm and fluorescencespectra with Ex/Em 495/517 were recorded.

Analytical UPLC:

UPLC-UV traces were obtained on a Waters H-class instrument equippedwith a Quaternary Solvent Manager, a Waters autosampler and a Waters TUVdetector connected to a 3100 mass detector with an Acquity UPLC-BEH C181.7 μm, 2.1×50 mm RP column with a flow rate of 0.6 mL/min. Thefollowing gradient was used: Method B: (A=H₂O+0.1% TFA, B=MeCN+0.1% TFA)5-95% B 0-3 min, 95% B 3-5 min. UPLC-UV chromatograms were recorded at220 nm.

Preparative HPLC was performed on a Gilson PLC 2020 system (Gilson Inc.,WI, Middleton, USA) using a Macherey-Nagel Nucleodur C18 HTec Spumcolumn (Macherey-Nagel GmbH & Co. Kg, Düren, Germany). The followinggradient was used: Method C: (A=H2O+0.1% TFA, B=MeCN+0.1% TFA) flow rate32 mL/min, 10% B 0-5 min, 10-100% B 5-35 min, 100% B 35-40 min. MethodD: (A=H2O+0.1% TFA, B=MeCN+0.1% TFA) 10% B 0-5 min, 10-100% B 5-50 min,100% B 50-55 min.

Analytical HPLC-MSMS:

Peptides were analyzed by a Ultimate 3000 nanoLC system (ThermoScientific, Waltham, Mass., USA) connected to an LTQ Orbitrap XL massspectrometer (Thermo Scientific). LC separations were performed on acapillary column (Acclaim PepMap100, C18, 3 μm, 100A, 75 μm i.d.×25 cm,Thermo Scientific) at an eluent flow rate of 300 nL/min. The followinggradient was used: Method E: (A=H2O+0.1% formic acid, B=MeCN+0.1% formicacid) 3-50% B 0-50 min Mass spectra were acquired in a data-dependentmode with one MS survey scan with a resolution of 30,000 (LTQ OrbitrapXL) or 60,000 (Orbitrap Elite) and MS/MS scans of the five or 5 mostintense precursor ions in the linear trap quadrupole, respectively.

Column chromatography was performed on silica gel (Acros Silica gel 60Å, 0.035-0.070 mm).

High resolution mass spectra (HRMS) were measured on an Acquity UPLCsystem and a LCT Premier™ (Waters Micromass, Milford, Mass., USA)time-of-flight mass spectrometer with electrospray ionization usingwater and acetonitrile (10-90% gradient) with 0.1% formic acid aseluent.

NMR spectra were recorded with a Bruker Ultrashield 300 MHz spectrometer(Bruker Corp. Billerica, Mass., USA) at ambient temperature. Thechemical shifts are reported in ppm relatively to the residual solventpeak.

Reagents and solvents were, unless stated otherwise, commerciallyavailable as reagent grade and did not require further purification.Resins and Fmoc-protected amino acids were purchased from IRIS BioTEch(Marktredwitz, Germany) or Novabiochem (Darmstadt, Germany).

SPPS was either carried out manually or with an Activo-P11 automatedpeptide synthesizer (Activotec, Cambridge, UK) via standard Fmoc-basedconditions (Fast-moc protocol with HOBt/HBUT conditions).

Example 2: Synthesis of Tyrosine Derivatives 1, 2, 3, 4, and 5

2.1 Synthesis of 3-formyl-L-tyrosine (1)

The synthesis of 1 was performed according to a known procedure inliterature (Jung and Lavaroza (1997), J Org Chem, 62: 1553-1555;Banerjee et al. (2010), ACS chemical biology 5: 777-785).

N-[(1,1-dimethylethoxy)carbonyl]-L-tyrosine (7)

To a solution of L-tyrosine (6, 1 g, 5.5 mmol) in 1/1 dioxane/water (50mL), triethylamine (1.16 mL, 8.28 mmol) was slowly added. The reactionwas cooled to 0° C. with an ice/water bath and di-tert-butyl dicarbonate(1.32 g, 6.07 mmol) was added in two steps. After 1 h at 0° C., thetemperature was slowly increased to ambient temperature and the mixturewas stirred for further 24 h. Dioxane was removed under reduced pressureand the aqueous solution mixed with 25 mL saturated NaHCO₃, washed withethyl acetated, acidified to pH 1 with 1N HCl, extracted with ethylacetate and the organic extracts were washed with brine, dried overMgSO4 and evaporated to give N-Boc-L-tyrosine (7) as a white foam (1.471g, 95%) which was used in the next step without further purification.Analytical data matched the literature (Jung and Lavaroza (1997), J OrgChem, 62: 1553-1555).

N-[(1,1-dimethylethoxy)carbonyl]-3-(3-formyl-4-hydroxyphenyl)-L-alanine(8)

To a suspension of 7 (2.00 g, 7.12 mmol) in chloroform (30 mL) and water(0.256 mL, 14.13 mmol) powdered sodium hydroxide (1.71 g, 42.72 mmol)was added and the mixture was refluxed for 4h. Two additional portionsof powdered sodium hydroxide (each 0.42 g, 10.68 mmol) were added after1 and 2 h. After 8 h at reflux, the reaction was cooled to ambienttemperature, diluted with water and ethyl acetate (15 mL each), theorganic layer discharged, the aqueous layer acidified to pH1 with 1 NHCl and back-extracted with ethyl acetate. The organic layers werewashed with brine, dried over MgSO₄ and concentrated. Flash columnchromatography (silica gel, 12/1 CHCl₃/MeOH, 1% acetic acid) gavecompound 8 (0.49 g, 23%). Analytical data matched the literature (Jungand Lavaroza (1997), J Org Chem, 62: 1553-1555).

3-formyl-L-tyrosine (1)

Compound 8 (0.49 g, 1.6 mmol) was dissolved in 4 mL CH₂Cl₂. TFA (4 mL)was added slowly at 0° C. and the mixture was warmed to ambienttemperature within 2 h. The solvent was removed at high vacuum.Preparative HPLC (method C) gave compound 1 as TFA salt (0.29 g, 80%,18% TFA salt). The TFA salt content was determined by ¹⁹F NMR andtetrafluoroethylene as standard. ¹H NMR (300 MHz, D₂O): δ 9.81 (s, 1H,CHO), 7.52 (d, J=2.4 Hz, 1H, CH_(phenyl)), 7.40 (dd, J=8.6, 2.3 Hz, 1H,CH 6.90 (d, J=8.6 Hz, 1H, CH_(phenyl)), 4.13 (t, J=6.6 Hz, 1H, CH), 3.15(m, 2H, CH₂). ¹³C NMR (75 MHz, D₂O): δ 197.18, 171.68, 159.21, 138.07,134.02, 126.03, 120.97, 117.73, 54.18, 34.48.

2.2 Synthesis of 3-nitro-L-tyrosine (2) and 3-azido-L-tyrosine (3)

3-nitro-L-tyrosine (2)

L-tyrosine (6, 2.00 g, 11 mmol) was added to 10 mL HOAc, the suspensioncooled to 0° C. and HNO₃ (1.47 mL, 11 mmol, 7.5 N) was slowly added. Assoon as 6 dissolved completely (after 4h), the reaction was stopped byadding 2.5 mL H₂O followed by neutralisation with 25% NH₃ solution. Theresultant solution was filtrated, the filtrate lyophilized and subjectedto HPLC purification (method C) to give compound 2 as TFA salt (1.38 g,44%, 51% TFA salt). The TFA salt content was determined by ¹⁹F NMR andtetrafluoroethylene as standard. ¹H NMR (300 MHz, D₂O): δ 7.89 (d, J=2.3Hz, 1H, CH_(phenyl)), 7.43 (dd, J=8.7, 2.3 Hz, 1H, CH_(phenyl)), 7.03(d, J=8.7 Hz, 1H, CH_(phenyl)), 4.18 (t, J=6.6 Hz, 1H, CH), 3.31-3.04(m, 2H, CH₂). ¹³C NMR (75 MHz, D₂O): δ 171.11, 152.74, 138.21, 133.85,126.40, 125.76, 120.19, 53.68, 34.23.

3-amino-L-tyrosine (9)

Compound 2 (1.38 g, 4.86 mmol) was dissolved in 100 mL H₂O and 500 μLconc. HCl. The solution was supplemented with Pd/BaSO₄ (40 mg, 5%catalyst loading) and the mixture incubated at ambient temperature for12 h under H2 atmosphere. After filtration of the catalyst and removalof the solvent in vacuo, the product 9 was obtained in quantitativeyield as TFA salt (18% TFA salt content). The TFA salt content wasdetermined by ¹⁹F NMR and tetrafluoroethylene as standard. ¹H NMR (300MHz, D₂O): δ 7.42-7.15 (m, 2H, CH_(phenyl)), 7.05-6.89 (m, 1H,CH_(phenyl)), 4.11 (t, J=6.5 Hz, 1H, CH), 3.24-3.06 (m, 2H, CH₂). ¹³CNMR (75 MHz, D₂O): δ 171.91, 149.37, 131.23, 126.32, 124.68, 117.84,116.79, 54.47, 34.61.

3-azido-L-tyrosine (3)

3-amino-L-tyrosine (9, 0.696 g, 3.21 mmol) was dissolved in 6 mL 0.5 MHCl and a solution of NaNO₂ (0.221 g, 3.21 mmol) in 1 mL ice-cold H₂Owas slowly added at 0° C. After 20 minutes, 3 mL of a solution of NaN₃(0.560 g, 8.62 mmol) in H₂O were added within 30 minutes and stirred at0° C. for another 8 h. The grey precipitate was isolated and purified bypreparative HPLC (method C) to give pure compound 3 (0.290 g, 41%). ¹HNMR (300 MHz, D₂O): δ 6.95 (d, J=2.0 Hz, 1H, CH_(phenyl)) 6.89-6.79 (m,2H, CH_(phenyl)), 4.06 (t, J=6.5 Hz, 1H, CH), 3.19-2.95 (m, 2H, CH₂).¹³C NMR (75 MHz, D₂O): δ 172.04, 146.44, 127.24, 127.07, 126.58, 120.38,116.86, 54.51, 34.83

2.3 Synthesis of 3-Iodo-L-tyrosine (4)

The synthesis of 4 was performed according to a known procedure inliterature (Cochrane et al. (2012), Org. Lett., 14: 2402-2405.

L-tyrosine (6, 5.00 g, 27.5 mmol) was dissolved in conc. NH₄OH (500 mL)and cooled to 0° C. Iodine (7.00 g, 27.5 mmol) was dissolved in ethanol(95%, 100 mL) and added dropwise within 1 h to the tyrosine solution andstirred for 2 additional hours. The solution was concentrated to avolume of approx. 150 mL. It was acidified to pH 4.5 and cooled to 0° C.After one hour at 0° C., the formed crystals were collected and stirredin acetone for two hours. The product was collected to yield 4 as a greysolid (5.40 g, 63%). ¹H NMR (300 MHz, D₂O): δ 7.58 (d, J=2.3 Hz, 1H,CH_(phenyl)), 7.06 (dd, J=8.4, 2.2 Hz, CH_(phenyl)), 6.81 (d, J=8.3 Hz,CH_(phenyl)) 4.01 (t, J=6.5 Hz, 1H, CH), 3.14-2.90 (m, 2H, CH₂). ¹³C NMR(75 MHz, D₂O): δ 172.26, 154.56, 139.81, 130.69, 115.29, 83.67, 75.88,34.26.

2.4 Synthesis of O-Propargyl-L-Tyrosine (5)

The synthesis of 5 was performed according to a known procedure inliterature (Milles et al. (2012), JAGS., 134: 5187-5195.

Intermediate 10

7 (5.02 g, 17.8 mmol) and K₂CO₃ (7.39 g, 53.5 mmol) were suspended indry DMF (30 mL).

Propargylbromide (80% in toluene; 5.76 mL, 53.5 mmol) was added dropwiseand the reaction mixture was stirred at room temperature for 20 hours.H₂O (100 mL) and Et²O (100 mL) were added and the two phases separated.The aqueous layer was extracted with Et₂O, the combined org. phasesdried over MgSO₄ and evaporated to yield 10 as a yellow oil which wasused in the next step without further purification (6.02 g, 94%).

Intermediate 11

Acetyl chloride (7.27 g, 6.58 mL, 92.6 mmol) was slowly added toanhydrous methanol (55 mL) at 0° C. This mixture was then added tocompound 10 (6.02 g, 16.86 mmol), allowed to warm to ambient temp. Andstirred for additional 16 hours. All volatile components were removed invacuum to give HCl salt of 11 as a white solid which was used in thenext step without further purification (4.01 g, 80%).

O-propargyl-L-tyrosine (5)

11 (4.01 g, 13.63 mmol) was dissolved in methanol (15 mL) and aqueous 2NNaOH (20 mL) was added slowly. The mixture was acidified carefully withconc HCl to pH 3 and kept overnight at 4° C. A white precipitate formedwhich was filtered off and dried in the vacuum to yield the HCl-salt ofcompound 5 (3.05 g, 88%). ¹H NMR (300 MHz, DMSO-d₆): δ 7.20 (d, J=8.2Hz, 2H, CH_(phenyl)), 6.90 (d, J=8.3 Hz, 2H, CH_(phenyl)), 4.75 (d,J=2.4 Hz, 2H, CH₂), 3.56 (t, J=2.4 Hz, 1H, CH), 3.45 (dd, J=7.8, 4.6 Hz,1H, CH), 3.08 (dd, J=14.4m 4.6 Hz, 1H, CH), 2.85 (dd, J=14.4, 7.9 Hz,1H, CH).

2.5 Synthesis of3-(N-iminoacetyl-N′-D-biotinyl-3,6-dioxaoctane,1,8-diamine)-tyrosine(12)

Biotin-hydroxylamine (20 mg, 0.04 mmol) was dissolved in 1 mL NH₄OAc pH4.5, 3-formyl-L-tyrosine 1 was added (9.34 mg 0.04 mmol) and thesolution incubated at 37° C., 200 rpm for 4 h. The reaction mixture waspurified by preparative HPLC (method D). The oxime 12 was obtained witha yield of 71% (20 mg, 0.03 mmol). ¹H-NMR (300 MHz, D₂O): δ 8.38 (s, 1H,ONCH), 7.24 (d, J=2.2 Hz, 1H, CH_(phenyl)), 7.17 (dd, J=8.5, 2.2 Hz, 1H,CH_(phenyl)), 6.87 (d, J=8.4 Hz, 1H, CH_(phenyl)), 4.59 (s, 2H, COCH₂O),4.47-4.41 (m, 1H, CH), 4.27-4.21 (m, 1H, CH), 4.15 (t, J=6.2 Hz, 1H,CH), 3.54-3.45 (m, 4H OCH₂CH₂O), 3.41-3.32 (m, 6H, CH₂O, CH₂NH),3.21-3.00 (m, 5H, CH₂NHboc, CH, CH₂), 2.83 (dd, J₁=13, J₂=4.9, Hz 1H,CHH_(exo)S), 2.63 (d, J=13 Hz, 1H, CHH_(endo)S), 2.10 (t, J=7.2 Hz, 2H,CH₂CO), 1.63-1.32 (m, 4H, CH₂), 1.32-1.20 (m, 2H, CH₂).

Example 3: Synthesis of Peptide CF-Tub-Tag (13)

Peptide 8 (SEQ ID No. 3) was synthesized by standard Fmoc-basedchemistry in a linear synthesis on an Activotec peptide synthesizerfollowed by manual coupling of 5(6)-carboxyfluorescein. 0.1 mmol ofFmoc-L-Glu(tBu)-Wang resin (subst: 0.58 mmol/g) was added to a reactionvessel and synthesis performed with five-fold amino acid excess.Coupling was achieved by HOBt/HBTU/DIPEA addition. After the final aminoacid coupling, the fluorophore was coupled in a double couplingprocedure with 5 eq of 5(6)-carboxyfluorescein, HOBt, HBTU and DIPEA inDMF for 1 h. The peptide was cleaved off the resin by addition ofTFA/DTT/Tis/thioanisol (95/2/2/1) in 4 h. Subsequently, the cleavagecocktail was evaporated by N₂-flow and the peptide was precipitated bythe addition of ice-cold diethyl ether. The precipitate was spun down,dissolved in water and acetonitrile and purified by preparative HPLC(method D). The peptide was obtained with a yield of 8% (16 mg, 8 μmol);molar mass peptide=1850.6 Da; HRMS: m/z: 926.3065 [M+2H]²⁺ (calc. m/z:926.3165).

Example 4: TTL Expression and Purification

TTL (Canis lupus) having NCBI Accession number XP_540180.2 was expressedin E. coli (BL21DE3) as Sumo-TTL fusion protein with an N-terminalHis-Tag. Cells were induced with 0.5 mM IPTG and incubated at 18° C. for18 h. Lysis was performed in presence of Lysozyme (100 μg/ml), DNAse (25μg/ml) and PMSF (2 mM) followed by sonification (Branson® Sonifier; 16×8sec, 20% Amplitude) and debris centrifugation at 20.000 g for 30 min.His-Sumo-TTL was purified using a 5 ml His-Trap. For removal of theSumo-Tag, peak fractions were incubated with SenP2 protease at 4° C.overnight. A second His-Trap run then removed the Sumo fraction.Purified protein was then desalted on a PD10 column (GE Healthcare);buffer was exchanged to MES/K pH 6.8 (20 mM MES, 100 mM KCl, 10 mMMgCl₂). Protein aliquots were shock-frozen and stored at −80° C. at 0.8g/l.

Example 5: Determination of TTL Activity UsingCarboxyfluorescein-Peptide 13

Tyrosination reactions were performed in a 250 μL solution consisting of20 mM MES/K pH 7.0, 100 mM KCl, 10 mM MgCl₂, 2.5 mM ATP, 1 mM tyrosinederivative, 0.2 mM peptide, 1 μM TTL and 5 mM DTT in case of compound 1,2, 4 and 5 or 5 mM reduced glutathione in case of compound 3,respectively. The mixture was incubated at 37° C. and several aliquots(25 μL) were taken within 24 h, mixed with equal volumes of H₂O+0.1% TFAand subjected either to isocratic analytical HPLC equipped with afluorescence detector (Method A) or analytical UPLC-MS analysis.Quantities of substrate and product peptides were estimated from thecorresponding peak-area in the fluorescence or UV detection spectrum(Ex/Em: 495/517).

Example 6: Cloning

A nanobody was equipped with a C-terminal TTL derived tag (Tub-tag) andan N-terminal 6×His-Tag. The DNA coding sequence of the Tubulin A1Aderived Tub-tag peptide VDSVEGEGEEEGEE (SEQ ID No: 3) was added to theNanobody sequences via PCR using Forward Primer5′-GGGGCCATGGCCCATCATCACCATCACCATGATGTGCAGCTGCAGGAGTCT GGGGGAG-3′ (SEQID NO: 9) and Reverse Primer 5′-CCCCGAATTCTTATTCTTCGCCTTCTTCTTCGCCTTCGCCTTCCACGCTATCCACTGAGGAGACGGTGACC-3′ (SEQ ID NO: 10) and subclonedinto pHen6 bacterial expression vector using NcoI and EcoRI restrictionsites. Positive clones were verified by DNA sequencing.

Example 7: Nanobody-Tub-Tag Expression and Purification

Nanobody-Tub-tag fusion proteins were expressed in E. coli (JM109).Cells were induced with 0.5 mM IPTG and incubated at 18° C. for 18 h.Lysis was performed in presence of Lysozyme (100 μg/ml), DNAse (25μg/ml) and PMSF (2 mM) followed by sonification (Branson® Sonifier; 16×8sec, 20% Amplitude) and debris centrifugation at 20.000 g for 30 min.The protein was purified with an Äkta FPLC system using a 5 ml His-Trap(GE Healthcare) column, peak fractions were concentrated to 2 ml usingAmicon filter columns (Cut-off 3 kDa; (Millipore)) and subjected to sizeexclusion chromatography using a Superdex 75 column (GE Healthcare).Peak fractions were pooled and protein aliquots were shock-frozen andstored at −80° C. at 0.5 g/l. Note: Tub-tag is shown in SEQ ID No. 3.

Example 8: Ligation of Tyrosine Derivatives to Modified Nanobodies

See FIG. 24

Tyrosination reactions were performed in a 50 μL solution consisting of20 mM MES/K pH 7.0, 100 mM KCl, 10 mM MgCl₂, 2.5 mM ATP, 1 mM tyrosinederivative, 1 μM TTL, 5 μM nanobody and 5 mM reduced glutathione in caseof azide containing compounds or 5 mM DTT in case of other tyrosinederivatives, respectively. The mixture was incubated at 37° C. for 1-3h.

8.1 Tryptic Digest and MSMS Analysis of Tyrosinated Nanobodies

Nanobodies were tyrosinated as described in Example 8. Proteins wereseparated by SDS-PAGE. Protein bands of interest were excised, soakedwith 100 μL 50 mM (NH₄)₂CO₃/ACN 1:1 and incubated at 30° C. for 10 min.The supernatant was removed and the gel pieces were incubated in 50 mM(NH₄)₂CO₃ at 30° C. for further 10 min. The two incubation steps wererepeated until the pieces were colorless. Hereafter, the gel pieces weredehydrated by the addition of 25 μL ACN, the supernatant removed and thegels were dried under reduced pressure. In-gel digest was performed in atotal volume of 20 μL 50 mM (NH₄)₂CO₃ at 37° C. for 12 h using 0.05 μgTrypsin. 20 μL ACN+0.5% TFA were added, the mixture was incubated in anultrasonic bath, the supernatant transferred to LC glass vials, thesolvent was removed under reduced pressure and the residual peptidesresuspended in 6 μL 95% H₂O+0.1% TFA, 5% ACN+0.1% TFA solution. Peptideswere separated by HPLC and analysed by MSMS experiments.

8.2 Bioorthogonal Labeling of Tyrosinated Nanobodies:

Biotin Labeling

See FIG. 25

Nanobodies were tyrosinated as described in Example 8, above. Thereaction mixtures were rebuffered to 100 mM NH₄OAc, 100 mM NaCl pH 5.4(in case of reaction with biotin-hydroxylamine) or Dulbecco's PBS pH 7.4(in case of biotin-phosphines and biotin-dibenzylcyclooctynes) andincubated with 20-40 eq of biotin derivative at 20° C. -37° C. for 4-12h. Proteins were separated by SDS-PAGE and wet blotted onto anitrocellulose membrane using a Bio-Rad Mini-Protean Tetra System (250mA, 1 h). The membrane was blocked with Roti-Block (Carl Roth,Karlsruhe, Germany) for 1 h at ambient temperature and incubated for 1 hwith streptavidin peroxidase conjugate (Merck Millipore, Darmstadt,Germany) (1:2000) at ambient temperature. Immunodetection was performedwith WesternBright chemiluminescence solution (Western Bright ECL,Biozym Scientific, Hessisch Oldendorf, Germany) and a ChemiDoc™ XRS+ gelimaging system (Bio-Rad, Hercules, Calif., US).

Labelling with Fluorophores Alexa594®-Hydrazide Cy5-dibenzylcyclooctyneand Cy5-alkyne

See FIG. 26

Nanobodies were tyrosinated as described in Example 8, above. Thereaction mixtures were rebuffered to 100 mM NH₄OAc, 100 mM NaCl pH 6.0(in case of reaction with Alexa594®-hydrazides) or Dulbecco's PBS pH 7.4(in case of Cy5-dibenzylcyclooctynes) and incubated with 30 eq offluorophore at 20° C. -37° C. for 4-12h. In case of Cy5-alkyne, thereaction mixture was rebuffered 0.38 mmol K₂HPO₄ at pH 7.0 and 30 eq.fluorophore added. A aqueous solution of 0.1 eq Pd(OAc)₂[DMADHP]₂ and0.2 eq sodium-ascorbate was incubated at 37° C. for 10 minutes and addedto the protein mixture which was further incubated at 37° C. for 4h.Proteins were separated by SDS-PAGE and visualized by a ChemiDoc™ MP gelimaging system (Bio-Rad, Hercules, Calif., US) and a Fuji FLA-5000 laserimager (Alexa594®: 532 nm excitation, Cy5: 634 nm excitation,LPG-filter)(Fujifilm, Tokyo, Japan).

Pegylation by Staudinger-Phosphite Reaction

Nanobodies were tyrosinated as described in Example 8, above. Thereaction mixtures were rebuffered to 50 mM Tris, 100 mM KCl pH 8.5 andincubated with 40 eq. of tris(PEG750)phosphite at 37° C. for 24h.Proteins were separated by SDS-Page. PEGylated nanobodies were wetblotted onto a nitrocellulose membrane using a Bio-Rad Mini-ProteanTetra System (250 mA, 1h). A monoclonal anti PEG-B-47 antibody (Ancam,UK) and a secondary Goat Anti-Rabbit IgG H&L (HRP) (Abcam, UK) were usedfor detection.

Example 9: One Step Labeling

See FIG. 27

Labeling reactions were performed in a 150 μL solution consisting of 20mM MES/K pH 7.0, 100 mM KCl, 10 mM MgCl₂, 2.5 mM ATP, 1 mMtyrosine-biotin 12, 1 μM TTL, 5 μM nanobody and 5 mM DTT. The mixturewas incubated at 37° C. for 20h. Proteins were separated by SDS-PAGE andwet blotted onto a nitrocellulose membrane using a Bio-Rad Mini-ProteanTetra System (250 mA, 1h). The membrane was blocked with Roti-Block(Carl Roth, Karlsruhe, Germany) for 1 h at ambient temperature andincubated for 1 h with streptavidin peroxidase conjugate (MerckMillipore, Darmstadt, Germany) (1:2000) at ambient temperature.Immunodetection was performed with WesternBright chemiluminescencesolution (Western Bright ECL, Biozym Scientific, Hessisch Oldendorf,Germany) and a ChemiDoc™ XRS+ gel imaging system (Bio-Rad, Hercules,Calif., US). See FIG. 22.

Example 10: Abbreviations

-   Da Dalton-   DIC diisopropylcarbodiimide-   DI PEA diisopropylethylamine-   DMADHP N,N-dimethyl-2-amino-4,6-dihydropyrimidine-   DMF N,N-dimethylformamide-   DTT dithiotreitol-   eq equivalents-   Em emission wavelength in nanometer-   Ex excitation wavelength in nanometer-   Fmoc fluorenylmethyloxycarbonyl-   HBTU N,N,N′,N′-Tetramethyl-O-(1H-benzotriazol-1-yl)uranium    hexafluorophosphate-   HOAc acetic acid-   HOBt hydroxybenzotriazole-   HPLC high performance liquid chromatography-   HRMS high resolution mass spectrometry-   LC liquid chromatography-   MeCN acetonitrile-   MHz megahertz-   SDS-PAGE sodium dodecyl sulfate polyacrylamide gel electrophoresis-   TFA trifluoroacetic acid-   TIS triisopropylsilane-   Tub-tag Tubulin derived TTL recognition sequence-   Tub-tag labeling present invention-   UPLC ultra performance liquid chromatography-   UV ultraviolet

Example 11: Versatile and Efficient Site-Specific ProteinFunctionalization by Tubulin Tyrosine Lipase

Here we present a novel chemoenzymatic approach for simple and fastsite-specific protein labeling. We repurposed tubulin tyrosine ligase(TTL) to attach various unnatural tyrosine derivatives as smallbioorthogonal handles to recombinant proteins containing a short tubulinderived recognition sequence (Tub-tag). This novel strategy enables abroad range of chemoselective C-terminal protein modifications forapplications in biochemistry, cell biology and beyond as demonstratedfor the site-specific labeling of nanobodies.

Site-specific functionalization of proteins is crucial for a plethora ofapplications throughout the life sciences. Fluorescent proteins andself-labeling strategies like SNAP-¹ and HALO-² tagging have becomeindispensable tools for cell biologists to analyze intracellularactivity and localize proteins of interest. The genetic fusion of GFP orself-labeling protein tags is straightforward, however, the size andbiochemical nature of the attachment may affect the properties andapplication of the chimeric protein³.

Protein trans-splicing, expressed protein ligation as well as ambersuppression and auxotrophic expression in combination with bioorthogonallabeling⁴ are prominent tools that allow the placement of small tags andmodifications to proteins. However, low expression yields, the need ofprotein engineering and impaired protein folding are limiting factors ofthese techniques. In addition, chemoenzymatic approaches find increasingattention for the site-specific addressability of proteins using shortand specific recognition tags in conjunction with respective enzymessuch as trypsin⁵, Sortase A⁶, phosphopantetheinyl-transferase (PPTase)⁷,biotin ligase⁸, lipoic acid ligase⁹, and formylglycine generatingenzyme¹⁰.

Together, these chemoenzymatic systems open up broad possibilities forsubsequent chemoselective and site-specific labeling, but still havechemical limitations. These challenges include large and hydrophobicsubstrates for the enzymatic reaction that may affect the protein ofinterest (PPTase, lipoic acid ligase, biotin ligase). Moreover, reactionreversibility and product hydrolysis necessitate a high excess ofcatalyst and substrate (Sortase labeling, formylglycine generatingenzyme, trypsin). In particular the targeted incorporation of unnaturalfunctional groups often requires extensive enzyme engineering to improvethe overall reaction efficiency.

Here we present a novel and fast method for the site-specific labelingof proteins that combines the use of small unnatural amino acids asbioorthogonal handles and the technical advantages of chemoenzymaticlabeling. The technique, termed Tub-tag labeling, is based on theenzymatic ligation of easy to synthesize, small tyrosine derivatives tothe C-terminus of a fourteen amino acid hydrophilic recognition tag(termed Tub-tag) by tubulin tyrosine ligase (TTL, FIG. 5a ). In nature,TTL catalyzes the post-translational attachment of tyrosine to theC-terminus of α-tubulin, which is involved in the regulation ofmicrotubule homeostasis^(11,12). Interestingly, TTL also utilizestyrosine derivatives for tubulin modification¹³. To test whether TTL mayconjugate unnatural tyrosine derivatives to the isolated Tub-tagpeptide, mimicking the C-terminus of tubulin, we performed an initialligation experiment with 3-N₃-L-tyrosine (3) and 3-formyl-L-tyrosine(1). For this purpose, we first synthesized a 5,6-carboxyfluoresceinlabeled Tub-tag peptide (CF-Tub-tag) by standard solid phase peptidesynthesis (SPPS), used it for Tub-tag labeling with 1 and 3 (TTL:peptide1:200) and analyzed the reaction process by isocratic HPLC (FIGS. 5b andc for 3, FIGS. 5d and e for 1). After 120 min of incubation at 37° C.the conjugate yield with 1 and 3 was 63% and 80%, respectively.

Next, we tested whether the Tub-tag labeling can be transferred tounrelated proteins of interest. For proof-of-principle we usedcamel-derived, single-domain nanobodies¹⁴ that are used as analyticaltools in biochemistry as well as for the intracellular recognition andmanipulation of antigens in cell biology^(15,16). We fused the Tub-tagsequence to the C-terminus of a GFP-specific nanobody (GBP4¹⁷) andperformed TTL-mediated labeling experiments. Tryptic digest followed byHPLC-MS/MS experiments showed the successful C-terminal addition oftyrosine (6), 3-N₃-L-tyrosine (3), 3-formyl-L-tyrosine (1),3-NH₂-L-tyrosine (9) and 3-NO2-L-tyrosine (2) (FIG. 8). Next, wecombined the incorporation of 3 with subsequent strain-promotedazide-alkyne cycloaddition (SPAAC)¹⁸ for the conjugation of aDBCO-biotin derivative (FIG. 6). Using a ratio of 1:5 TTL/GBP4 at 37° C.we found that 82% of GBP4 was converted after one hour, whereas a ratioof 1:10 TTL/GBP4 delivered 71% C-terminally modified GBP4. Extending theligation time to three hours resulted in 99% and 88% conversions at 1:5and 1:10 TTL/GBP4 ratios, respectively. The incorporation of3-formyl-L-tyrosine (1) could be achieved with similar efficiencies. Tofurther validate the modularity of the Tub-tag labeling concept, weperformed fluorescent labeling by SPAAC (FIG. 10) and employed a varietyof well-established bioorthogonal reactions including theStaudinger-ligation¹⁹ (FIG. 11) and the Staudinger-Phosphite reaction²⁰(FIG. 12) to 3-N3-L-tyrosine (3). In addition, hydrazone (FIG. 13) andoxime forming reactions²¹ (FIG. 14) were applied on site-specificallyincorporated 3-formyl-L-tyrosine (1). This allowed us to incorporatedifferent biotin derivatives, fluorophores and even enabled the branchedPEGylation of GBP4 (FIG. 12). After having established thischemoenzymatic modification, we used this method for the fluorescent andbiotin labeling of another GFP-specific nanobody (GBP1¹⁷) (FIG. 15). Totest whether TTL-mediated modification yields functional nanobodies, weused GBP1 for biochemical and cell biological applications. Following3-N3-L-tyrosine (3) incorporation via TTL, GBP1 was biotinylated usingDBCO-biotin as described above and immobilized on Streptavidin-coatedmagnetic beads (Figure. 7a). These beads were then used forimmunoprecipitation of GFP from HEK cell lysates. Subsequent westernblot analysis demonstrated specific GFP pulldown compared to controlswith mock transfected cell lysate and non-functionalized beads (Figure.7b).

We subsequently studied, whether site-specifically labeled GBP1 can beused to stain cellular structures in immunofluorescence experiments. Wehave previously used this GFP-binding nanobody as a staining reagent forsuper-resolution microscopy techniques²². The higher resolution imposesnew requirements on detection reagents and, thus, using the smallestpossible immunofluorescent binding reagents is important to unleash thefull potential of super-resolution microscopy²³. Here, following3-formyl-L-tyrosine (1) incorporation via TTL, GBP1 was labeled withAlexa594 dye using oxime forming reaction (FIG. 7c ). HeLa cellsexpressing GFP-LaminB1, which localizes at the interior of the nuclearenvelope and forms the nuclear lamina, were stained with GBP1-Alexa594.3D-SIM super-resolution microscopy then revealed laminar colocalizationof the GBP1 staining reagent at high resolution, indicating functionalbinding to GFP in this cellular context (FIGS. 7d, e and f ). Similarresults were obtained with GFP-PCNA and the detection of subnuclear DNAreplication sites (FIG. 16).

In summary, we introduce Tub-tag labeling for simple, site-specificmodification of proteins. We show TTL-mediated, chemoenzymatic ligationof unnatural tyrosine derivatives like 3-N₃-L-tyrosine (3) and3-formyl-L-tyrosine (1) with up to 99% efficiency using moderate enzymeconcentrations and short reaction times. These modified tyrosineresidues then serve as bioorthogonal handles for a variety ofwell-established chemoselective labeling reactions. The overall labelingefficiency under mild reaction conditions yields homogeneously modifiedand functional proteins as demonstrated with nanobodies forimmunoprecipitation and super-resolution microscopy. Thus, Tub-taglabeling endows recombinant antibodies—and proteins in general—withnovel properties to explore and manipulate cellular functions withpossible applications in biotechnology as well as in diagnosis andtherapy.

Example 12: TTL Expression and Purification

TTL (Canis lupus) coding sequence was amplified from a mammalianexpression vector24, cloned into a pET28-SUMO3 (EMBL-Heidelberg, ProteinExpression Facility) and expressed in E. coli BL21(DE3) as Sumo-TTLfusion protein with an N-terminal His-Tag. Cells were induced with 0.5mM IPTG and incubated at 18° C. for 18 h. Lysis was performed inpresence of Lysozyme (100 μg/ml), DNAse (25 μg/ml) and PMSF (2 mM)followed by sonification (Branson® Sonifier; 16×8 sec, 20% amplitude)and debris centrifugation at 20.000 g for 30 min. His-Sumo-TTL waspurified using a 5 ml His-Trap. Purified protein was then desalted on aPD10 column (GE Healthcare); buffer was exchanged to MES/K pH 6.8 (20 mMMES, 100 mM KCl, 10 mM MgCl2). Protein aliquots were shock-frozen andstored at −80° C. at 2.7 g/l.

Example 13: Determination of TTL Activity Using CF-Tub-Tact Peptide 13

Tyrosination reactions were performed in a 250 μL solution consisting of20 mM MES/K pH 7.0, 100 mM KCl, 10 mM MgCl2, 2.5 mM ATP, 1 mM tyrosinederivative, 0.2 mM CF-Tub-tag 13, 1 μM TTL and 5 mM DTT in case ofcompound 2 or 5 mM reduced glutathione in case of compound 1,respectively. The mixture was incubated at 37° C. and several aliquots(25 μL) were taken, mixed with equal volumes of H₂O+0.1% TFA andsubjected to isocratic analytical HPLC equipped with a fluorescencedetector (Method: A=H2O+0.1% TFA, B=MeCN+0.1% TFA; 35% B, 0-15 min,10-100% B 15-17 min, 100% B 17-22 min, 100-35% B 22-25 min and 35% B25-30 min.). Quantities of substrate and product peptides were estimatedfrom the corresponding peak-area in the fluorescence detection spectrum(Ex/Em: 495/517).

Example 14: Nanobody-Tub-Tag Expression and Purification

Nanobody-Tub-tag fusion proteins were expressed in E. coli (JM109).Cells were induced with 0.5 mM IPTG and incubated at 18° C. for 18 h.Lysis was performed in presence of Lysozyme (100 μg/ml), DNAse (25μg/ml) and PMSF (2 mM) followed by sonication (Branson® Sonifier; 16×8sec, 20% Amplitude) and debris centrifugation at 20.000 g for 30 min.The protein was purified with an Äkta FPLC system using a 5 mL His-Trap(GE Healthcare, USA) column, peak fractions were concentrated to 2 mlusing Amicon filter columns (cut-off 3 kDa; (Merck Millipore, Germany)and subjected to size exclusion chromatography using a Superdex 75column (GE Healthcare, USA). Peak fractions were pooled and proteinaliquots were shock-frozen and stored at −80° C.

Example 15: TTL Reaction on GBP4 Followed by Tryptic Digest and MSMSAnalysis

Tyrosination reactions were performed in a 50 μL solution consisting of20 mM MES/K pH 7.0, 100 mM KCl, 10 mM MgCl₂, 2.5 mM ATP, 1 mM tyrosinederivative, 1 μM TTL, 5 μM nanobody and 5 mM reduced glutathione in caseof compound 3 and 5 mM DTT in case of compound 1, 2, 9 and tyrosine (6),respectively. The mixture was incubated at 37° C. for 24 h. Proteinswere separated by SDS-PAGE. Protein bands of interest were excised,soaked with 100 μL 50 mM (NH₄)₂CO₃/ACN 1:1 and incubated at 30° C. for10 min. The supernatant was removed and the gel pieces were incubated in50 mM (NH₄)₂CO₃ at 30° C. for further 10 min. The two incubation stepswere repeated until the pieces were colourless. Hereafter, the gelpieces were dehydrated by the addition of 25 μL ACN, the supernatantremoved and the gels were dried under reduced pressure. In-gel digestwas performed in a total volume of 20 μL 50 mM (NH₄)₂CO₃ at 37° C. for12 h using 0.05 μg trypsin (Thermo Fisher Scientific, USA). 20 μLACN+0.5% TFA was added, the mixture incubated in an ultrasonic bath, thesupernatant transferred to LC glass vials, the solvent removed underreduced pressure and the residual peptides resuspended in 6 μL 95%H₂O+0.1% TFA, 5% ACN+0.1% TFA solution. Peptides were separated by HPLCand analyzed by MSMS experiments.

Example 16: Chemoenzymatic Addition of Tyrosine Derivatives toNanobodies

Tyrosination reactions were performed in a 150 μL solution consisting of20 mM MES/K pH 7.0, 100 mM KCl, 10 mM MgCl₂, 2.5 mM ATP, 1 mM tyrosinederivative, 0.1-1 μM TTL, 5 μM nanobody and 5 mM reduced glutathione incase of compounds containing azides or 5 mM DTT for all otherderivatives, respectively. The mixture was incubated at 37° C. for 1-3h.

Example 17: SPAAC to Sulfo-Cy5-DBCO or Biotin-DBCO

Tyrosination reactions were performed as described in Example 16 usingcompound 3, 5 mM reduced glutathione and a ratio of 10:1 GBP4/TTL for 3h. The reaction mixtures were rebuffered to Dulbecco's PBS pH 7.4 andincubated with 30 eq. of Sulfo-Cy5-DBCO (Jena Bioscience GmbH, Germany)or DBCO-PEG4-biotin (Jena Bioscience GmbH, Germany) at 30° C. for 4 h.Proteins were separated by SDS-PAGE. Biotinylated nanobodies were wetblotted onto a nitrocellulose membrane using a Bio-Rad Mini-ProteanTetra System (250 mA, one hour). A streptavidin peroxidase conjugate(Merck Millipore, Germany) was used for detection. Fluorescently labelednanobodies were visualized by a Fuji FLA-5000 laser imager (634 nmexcitation, LPG-filter) (Fujifilm, Japan).

Example 18: Staudinger-Ligation

Tyrosination reactions were performed as described in Example 16 usingcompound 3, 5 mM reduced glutathione and a ratio of 10:1 GBP4/TTL for 3h. The reaction mixtures were rebuffered to Dulbecco's PBS pH 7.4 andincubated with 40 eq. of biotin-phosphine (BIOMOL GmbH, Germany) at 37°C. for 24 h. Proteins were separated by SDS-PAGE. Biotinylatednanobodies were wet blotted onto a nitrocellulose membrane using aBio-Rad Mini-Protean Tetra System (250 mA, 1 h). A streptavidinperoxidase conjugate (Merck Millipore, Germany) was used for detection.

Example 19: Staudinger-Phosphite Reaction

Tyrosination reactions were performed as described in Example 16 usingcompound 3, 5 mM reduced glutathione and a ratio of 10:1 GBP4/TTL for 3h. The reaction mixtures were rebuffered to 50 mM Tris pH 8.5, 100 mMKCl and incubated with 40 eq. of tris(PEG750)phosphite (14) at 37 C for24 h. Proteins were separated by SDS-PAGE. PEGylated nanobodies were wetblotted onto a nitrocellulose membrane using a Bio-Rad Mini-ProteanTetra System (250 mA, 1h). A monoclonal anti PEG-B-47 antibody (Abcam,UK) and a secondary Goat Anti-Rabbit IgG H&L (HRP) (Abcam, UK) were usedfor detection.

Example 20: Hydrazone and Oxime Forming Reactions

Tyrosination reactions were performed as described in Example 16 withcompound 1, 5 mM DTT and a ratio of 10:1 GBP4/TTL for 3 h. The reactionmixtures were rebuffered to 50 mM MES/K pH 6.0, 100 mM KCl and incubatedwith 30 eq of Alexa594-hydrazide (Thermo Fisher Scientific, USA) orhydroxylamine-biotin (15) at 37° C. for 4 h. Proteins were separated bySDS-PAGE. Biotinylated nanobodies were wet blotted onto a nitrocellulosemembrane using a Bio-Rad Mini-Protean Tetra System (250 mA, 1 h). Astreptavidin peroxidase conjugate (Merck Millipore, Germany) was usedfor detection. Fluorescently labeled nanobodies were visualized by aFuji FLA-5000 laser imager (532 nm excitation, LPG-filter) (Fujifilm,Japan).

Example 21: Immunofluorescence

HeLa-Kyoto cells were maintained in DMEM supplemented with 10% fetalcalf serum and gentamycin at 50 μg/ml (PAA, Germany). Forimmunofluorescence experiments 10⁶ cells were seeded on gridded 18×18 mmcoverslips in a 6-well plate. Transfection with LaminB1-GFP encodingplasmid DNA (kind gift from Jan Ellenberg) was performed withLipofectamine 3000 (Life Technologies, USA) according to themanufacturers' instructions. 18 h post transfection, cells were washedwith PBST, fixed with 2% formaldehyde/PBS, and permeabilized with 0.5%Triton X-100/PBS. Next, cells were blocked with 2% BSA/PBST. Cells werethen incubated with Atto594 Tub-tag labeled GBP1 for 1 h, washed withPBST, DAPI stained (Life Technologies, USA) and mounted in Vectashieldanti-fading reagent (Vector Laboratories, USA) on object slides.High-resolution microscopy was performed with an DeltaVision OMX v3(Applied Precision, Slovakia) equipped with 405, 488 and 593 nm laserdiodes, a 100×/1.4 NA Plan-Apochromat oil objective lens (Olympus,Japan) and Cascade 11:512 EM CCD cameras (Photometrics, USA) asdescribed previously (Guizetti, J. et al. Cortical constriction duringabscission involves helices of ESCRT-III-dependent filaments. Science331, 1616-1620, doi:science.1201847 [pii] 10.1126/science.1201847(2011)). Line scan fluorescence intensity analysis was performed withImageJ.

Example 22: Streptavidin Pulldown Assay

HEK 293T cells were maintained in DMEM supplemented with 10% fetal calfserum and gentamycin at 50 μg/ml (PM, Germany). For pulldown experiments107 cells were seeded in p100 dishes. Transfection with eGFP encodingplasmid DNA peGFP-C1 (Life Technologies, Germany) was performed withpolyethylenimine (PEI, Sigma, USA) with 24 μg DNA per dish. Pulldownreagent was prepared by using biotinylated GBP1 (Tub-tag mediated). Forthis purpose, 200 μl slurry of Streptavidin-coated, magnetic beads(Dynabeads MyOne Streptavidin T1) were washed with PBS and then loadedwith 40 μg biotinylated GBP1 according to the manufacturers'instructions. Functionalized beads were equilibrated with IP buffer (0.5mM EDTA, 50 mM Tris/Cl pH 7.0, 150 mM NaCl). Whole cell lysates wereprepared using 200 μl lysis buffer (0.5 mM EDTA, 50 mM Tris/Cl pH 7.0,150 mM NaCl, 1% NP40, 2 mM PMSF, 1× Mammalian Protease InhibitorCocktail. 5% of lysate supernatants were collected as input samples. Theremaining sample was diluted to 1 ml using IP buffer and incubated with50 μl bead slurry for 4 h. After magnetic pulldown, 5% supernatant werecollected as flowthrough samples. For Coomassie staining and westernblotting 2% input, 2% flowthrough and 20% bead fractions were boiledwith Laemmli buffer at 95° C. and subjected to SDS-PAGE and transfer toa nitrocellulose membrane (Bio-Rad, USA). A monoclonal anti-GFP antibody(Roche, Switzerland) and HRP-conjugated anti-mouse IgG secondaryantibody (Jackson ImmunoResearch, USA) was used for detection.

Example 23: Confocal Microscopy

Transfection. HeLa cells were seeded at sub-confluent concentration onglass coverslips (Carl Roth, Germany) the day before PEI transfection(Sigma-Aldrich, USA) with 2 μg pENeGFP-PCNA1. After transfection, cellswere incubated for 18-24 h at 37° C., 5% CO2. Immunofluorescence. Cellswere fixed in 3.7% formaldehyde in PBS for 10 min, permeabilized with0.5% Triton X-100 (neoLab Migge Laborbedarf-Vertriebs, Germany) for 10min, and blocked in 2% bovine serum albumin (Sigma-Aldrich, UK) for 60min. For GFP labeling, cells were incubated for 60 min withGBP1-Tub-tag-Alexa594 (1:25 or 1:50) prior to extensive washing and DNAcounterstain with 1 μg/mL DAPI for 10 min. All steps except fixationwere carried out in PBS supplemented with 0.02% Tween 20 (PBST, CarlRoth, 9127.1) at room temperature. Glass coverslips were then mountedwith anti-fade Mowiol mounting medium (Sigma-Aldrich, UK).

Confocal Microscopy and Image Analysis. Imaging was carried out with aLeica SP5 II confocal point scanner (Leica Microsystems, Germany)equipped with two HyD hybrid detectors. Image acquisition was performedwith a ×60/1.4-0.6 NA Planapochromat oil immersion objective lens. Tovisualize DAPI, GFP and GBP1-Tub-tag-Alexa594, the 405, 488 and 561 nmexcitation lasers were used, respectively. 16 bit images were collectedand analyzed with Fiji2.

Example 24: Chemical Synthesis

Analytical HPLC was conducted on a SHIMADZU HPLC system (Shimadzu Corp.,Japan) with a SIL-20A autosampler, 2 pumps LC2 AAT, a 2489 UV/Visibledetector, a CTO-20A column oven and an RF-10 A X2 fluorescence detectorusing an Agilent Eclipse C18 5 μm, 250×4.6 mm RP-HPLC-column with a flowrate of 0.5 mL/min. The following gradient was used: Method A:(A=H₂O+0.1% TFA, B=MeCN+0.1% TFA) 35% B, 0-15 min, 10-100% B 15-17 min,100% B 17-22 min, 100-35% B 22-25 min and 35% B 25-30 min. UVchromatograms were recorded at 220 nm and fluorescence spectra withEx/Em 495/517 were recorded.

Analytical UPLC: UPLC-UV traces were obtained on a Waters H-classinstrument equipped with a Quaternary Solvent Manager, a Watersautosampler and a Waters TUV detector connected to a 3100 mass detectorwith an Acquity UPLC-BEH C18 1.7 μm, 2.1×50 mm RP column with a flowrate of 0.6 mL/min (Water Corp., USA). The following gradient was used:Method B: (A=H₂O+0.1% TFA, B=MeCN+0.1% TFA) 5-95% B 0-3 min, 95% B 3-5min. UPLC-UV chromatograms were recorded at 220 nm.

Preparative HPLC was performed on a Gilson PLC 2020 system (Gilson Inc.,WI, Middleton, USA) using a Macherey-Nagel Nucleodur C18 HTec Spurncolumn (Macherey-Nagel GmbH & Co. Kg, Germany). The following gradientwas used: Method C: (A=H2O+0.1% TFA, B=MeCN+0.1% TFA) flow rate 32mL/min, 10% B 0-5 min, 10-100% B 5-35 min, 100% B 35-40 min. Method D:(A=H2O+0.1% TFA, B=MeCN+0.1% TFA) 10% B 0-5 min, 10-100% B 5-50 min,100% B 50-55 min.

Analytical HPLC-MSMS: Peptides were analyzed by a Ultimate 3000 nanoLCsystem (Thermo Scientific, USA) connected to an LTQ Orbitrap XL massspectrometer (Thermo Scientific, USA). LC separations were performed ona capillary column (Acclaim PepMap100, C18, 3 μm, 100 Å, 75 μm i.d.×25cm, Thermo Scientific, USA) at an eluent flow rate of 300 nL/min. Thefollowing gradient was used: Method D: (A=H₂O+0.1% formic acid,B=MeCN+0.1% formic acid) 3-50% B 0-50 min Mass spectra were acquired ina data-dependent mode with one MS survey scan with a resolution of30,000 (LTQ Orbitrap XL) or 60,000 (Orbitrap Elite) and MS/MS scans ofthe five most intense precursor ions in the linear trap quadrupole,respectively. Column chromatography was performed on silica gel (AcrosSilica gel 60 Å, 0.035-0.070 mm). High resolution mass spectra (HRMS)were measured on an Acquity UPLC system and a LCT Premier™ (WatersCorp., USA) time-of-flight mass spectrometer with electrosprayionization using water and acetonitrile (10-90% gradient) with 0.1%formic acid as eluent. NMR spectra were recorded with a BrukerUltrashield 300 MHz spectrometer (Bruker Corp., USA) at ambienttemperature. The chemical shifts are reported in ppm relative to theresidual solvent peak.

Product yields were calculated based on ¹H-NMR spectra. TFA salt contentwas determined by ¹⁹F-NMR, tetrafluoroethylene as standard andconsidered in product yield calculation. Reagents and solvents were,unless stated otherwise, commercially available as reagent grade and didnot require further purification. Resins and Fmoc-protected amino acidswere purchased from IRIS BioTEch (Germany) or Novabiochem (Germany).

SPPS was either carried out manually or with an Activo-P11 automatedpeptide synthesizer (Activotec, UK) via standard Fmoc-based conditions(Fast-moc protocol with HOBt/HBUT conditions).

Example 25: Synthesis of 3-nitro-L-tyrosine (2), 3-amino-L-tyrosine (9)and 3-azido-L-tyrosine (3)

3-nitro-L-tyrosine (2)

L-tyrosine (6, 2.00 g, 11 mmol) was added to 10 mL HOAc, the suspensioncooled to 0° C. and HNO3 (1.47 mL, 11 mmol, 7.5 N) was slowly added.After 4 h (when the starting material was dissolved completely) thereaction was diluted with H2O (2.5 mL) followed by neutralization withNH3 solution (25%). The resultant solution was filtrated, the filtratelyophilized and subjected to HPLC purification (method C) to givecompound 2 as TFA salt (1.38 g, 44%). Analytical data matched theliterature (Seyedsayamdost, M. R., Argirevic, T., Minnihan, E. C.,Stubbe, J. & Bennati, M. J. Am. Chem. Soc. 131, 15729-15738 (2009)).

¹H-NMR (300 MHz, D2O): δ 7.89 (d, J=2.3 Hz, 1H, CH_(phenyl)), 7.43 (dd,J=8.7, 2.3 Hz, 1H, CH_(phenyl)), 7.03 (d, J=8.7 Hz, 1H, CH_(phenyl)),4.18 (t, J=6.6 Hz, 1H, CH), 3.31-3.04 (m, 2H, CH2); ¹³C-NMR (75 MHz,D₂O): δ 171.11, 152.74, 138.21, 133.85, 126.40, 125.76, 120.19, 53.68,34.23; ESI-HRMS (m/z): [M]⁺ calcd. for C₉H₁₂N₂O₅, 227.0660; found227.0674.

3-amino-L-tyrosine (9)

Compound 2 (1.38 g, 4.86 mmol) was dissolved in H₂O (100 mL) and conc.HCl (500 μL). The solution was supplemented with Pd/BaSO₄ (40 mg, 5%catalyst loading) and the mixture incubated at ambient temperature for12 h under H₂ atmosphere. After filtration of the catalyst and removalof the solvent in vacuo, the product 9 was obtained in quantitativeyield as TFA salt. Analytical data matched the literature(Seyedsayamdost, M. R., Argirevic, T., Minnihan, E. C., Stubbe, J. &Bennati, M. J. Am. Chem. Soc. 131, 15729-15738 (2009)).

¹H-NMR (300 MHz, D2O): δ 7.42-7.15 (m, 2H, CH_(phenyl)) 7.05-6.89 (m,1H, CH_(phenyl)), 4.11 (t, J=6.5 Hz, 1H, CH), 3.24-3.06 (m, 2H, CH₂);¹³C-NMR (75 MHz, D2O): δ=171.91, 149.37, 131.23, 126.32, 124.68, 117.84,116.79, 54.47, 34.61; ESI-HRMS (m/z): [M]⁺ calcd. for C₉H₁₃N₂O₃,197.0918; found 197.0910.

3-azido-L-tyrosine (3)

3-amino-L-tyrosine (9, 0.696 g, 3.21 mmol) was dissolved in 0.5 M HCl (6mL) and a solution of NaNO₂ (0.221 g, 3.21 mmol) in ice-cold H₂O (1 mL)was slowly added at 0° C. After 20 min, a solution of NaN₃ (0.560 g,8.62 mmol) in H₂O (3 mL) was added within 30 min and stirred at 0° C.for another 8 h. The grey precipitate was isolated and purified bypreparative HPLC (method C) to give pure compound 3 (0.290 g, 41%).

¹H-NMR (300 MHz, D₂O): δ 6.95 (d, J=2.0 Hz, 1H, CH_(phenyl)), 6.89-6.79(m, 2H, CH_(phenyl)), 4.06 (t, J=6.5 Hz, 1H, CH), 3.19-2.95 (m, 2H,CH2); ¹³C-NMR (75 MHz, D2O): δ 172.04, 146.44, 127.24, 127.07, 126.58,120.38, 116.86, 54.51, 34.83; ESI-HRMS (m/z): [M]⁺ calcd. for C₉H₁₁N₄O₃,223.0823; found 223.0830.

Example 26: Synthesis of 3-formyl-L-tyrosine (1)

The synthesis of 1 was performed according to a known procedure inliterature (Jung, M. E. & Lazarova, T. I. J. Org. Chem. 62, 1553-1555(1997); Banerjee, A. et al. ACS Chem. Biol. 5, 777-785 (2010)).

N-[(1,1-dimethylethoxy)carbonyl]-L-tyrosine (7)

To a solution of L-tyrosine (6, 1 g, 5.5 mmol) in 1/1 dioxane/water (50mL), triethylamine (1.16 mL, 8.28 mmol) was slowly added. The reactionwas cooled to 0° C. with an ice/water bath and di-tert-butyl dicarbonate(1.32 g, 6.07 mmol) was added in two steps. After 1 h at 0° C., thetemperature was slowly increased to ambient temperature and the mixturewas stirred for further 24 h. Dioxane was removed under reduced pressureand the aqueous solution mixed with saturated NaHCO₃ (25 mL), washedwith ethyl acetate, acidified to pH 1 with 1 N HCl, extracted with ethylacetate and the organic extracts were washed with brine, dried overMgSO₄ and evaporated to give Boc protected tyrosine 7 as a white foam(1.471 g, 95%) which was used in the next step without furtherpurification. Analytical data matched the literature (Jung, M. E. &Lazarova, T. I. J. Org. Chem. 62, 1553-1555 (1997)).

¹H-NMR (300 MHz, CDCl₃): δ 7.50-7.22 (m, 2H, CH_(phenyl)), 7.42 (dd,J=8.6, 2.3 Hz, 1H, CH_(phenyl)), 6.92 (d, J=8.4 Hz, 1H, CH_(phenyl)),5.11 (br, 1H, NH), 4.73-4.28 (m, 1H, CH), 3.32-2.90 (m, 2H, CH₂), 1.42(s, 9H, CH₃).

N-[(1,1-dimethylethoxy)carbonyl]-3-(3-formyl-4-hydroxyphenyl)-L-alanine(8)

To a suspension of 7 (2.00 g, 7.12 mmol) in chloroform (30 mL) and H₂O(0.256 mL, 14.13 mmol) powdered sodium hydroxide (1.71 g, 42.72 mmol)was added and the mixture was refluxed for 4 h. Two additional portionsof powdered sodium hydroxide (each 0.42 g, 10.68 mmol) were added after1 and 2 h. After 8 h at reflux, the reaction was cooled to ambienttemperature, diluted with water and ethyl acetate (15 mL each), theorganic layer discharged, the aqueous layer acidified to pH 1 with 1 NHCl and back-extracted with ethyl acetate. The organic layers werewashed with brine, dried over MgSO₄ and concentrated. Flash columnchromatography (silica gel, 12/1 CHCl₃/MeOH, 1% acetic acid) gavecompound 8 (0.49 g, 23%). Analytical data matched the literature (Jung,M. E. & Lazarova, T. I. J. Org. Chem. 62, 1553-1555 (1997)).

¹H-NMR (300 MHz, CDCl₃): δ 9.85 (s, 1H, CHO), 7.49-7.21 (m, 2H,CH_(phenyl)) 7.40 (dd, J=8.6, 2.3 Hz, 1H, CH_(phenyl)), 6.94 (d, J=8.4Hz, 1H, CH_(phenyl)), 5.10 (br, 1H, NH), 4.73-4.27 (m, 1H, CH),3.30-2.89 (m, 2H, CH₂), 1.40 (s, 9H, CH₃).

3-formyl-L-tyrosine (1)

Compound 8 (0.49 g, 1.6 mmol) was dissolved in CH₂Cl₂. TFA (4 mL) wasadded slowly at 0° C. and the mixture was warmed to ambient temperaturewithin 2 h. The solvent was removed at high vacuum. Preparative HPLC(method C) gave compound 1 as TFA salt (0.29 g, 80%). Analytical datamatched the literature (Jung, M. E. & Lazarova, T. I. J. Org. Chem. 62,1553-1555 (1997)).

¹H-NMR (300 MHz, D₂O): δ 9.81 (s, 1H, CHO), 7.52 (d, J=2.4 Hz, 1H,CH_(phenyl)), 7.40 (dd, J=8.6, 2.3 Hz, 1H, CH_(phenyl)), 6.90 (d, J=8.6Hz, 1H, CH) 4.13 (t, J=6.6 Hz, 1H, CH), 3.15 (m, 2H, CH₂); ¹³C-NMR (75MHz, D₂O): δ 197.18, 171.68, 159.21, 138.07, 134.02, 126.03, 120.97,117.73, 54.18, 34.48; ESI-HRMS (m/z): [M]⁺ calcd. for C₁₀H₁₂NO₄,210.0758; found 210.0760.

Example 27: Synthesis of tris(PEG750)phosphite 14

14 was synthesized based on a protocol by Nischan et al (Angew. Chem.Int. Ed. 52, 11920-11924 (2013)). Polyethylene glycomethylether wascarefully dried at 70° C. under high vacuum. Hexamethylphosphortriamide(1 eq., 0.135 mmol, 24.5 μL) was added to dry polyethyleneglycomethylether (3 eq., 0.406 mmol, 0.314 g) at 110° C. and stirredunder N2 stream for 72 h. The product was recovered as a whiteparaffinic solid (0.133 mmol, 0.311 g). In order to avoid hydrolysis ofthe product, no purification was done. Due to the chemoselectivecharacter of the Staudinger-phosphite reaction, impurities do notinterfere in the reaction and can be removed easily after theStaudinger-phosphite reaction.

¹H-NMR (400 MHz, [D]-acetonitrile): δ 3.58-3.57 (m, 198.9H, OCH₂CH₂O—),3.32 (s, 9H, OCH₃); ³¹P-NMR (400 MHz, [D]-acetonitrile): δ 140.

Example 28: Synthesis of hydroxylamine-biotin S2

D-biotin N-hydroxysuccinimide ester (16)

1-ethyl-3-(3-dimethylaminopropyl)carbodiimid (184 mg, 0.96 mmol) wasadded to a solution of D-biotin (200 mg, 0.82 mmol) andN-hydroxysuccinimid (102 mg, 0.89 mmol) in dry DMF (10 mL). The solutionwas stirred for 12 h at ambient temperature, concentrated and theproduct crystallized from 2-propanol to give succinimide ester 16 (261mg, 80). The product was used without further purification andanalytical data are in accordance with those reported in the literature(Gerard, E., Meulle, A., Feron, O. & Marchand-Brynaert, J. Bioorg. Med.Chem. Lett. 22, 586-590 (2012)).

¹H-NMR (300 MHz, DMSO): δ 6.41 (s, 1H, NH), 6.36 (s, 1H, NH), 4.35-4.26(m, 1H, CH), 4.18-4.11 (m, 1H, CH), 3.14-3.05 (m, 1H, CH), 2.89-2.75 (m,5H, 2×CH₂, CH), 2.64 (t J=7.4 Hz, 2H, CH₂), 2.60-2.55 (m, 1H, 3.32, CH),1.72-1.32 (m, 6H, 3×CH₂).

2-Amino-3′[(tert-butoxycarbonyl)amino]ethylene glycol diethyl ether (17)

To a solution of 2,2′-(ethylenedioxy)-bis(ethylamine) (4.07 g, 27.46mmol) and N,N-Diisopropylethylamine (1.56 mL, 9.17 mmol) in dry CH₂Cl₂(50 mL) at ambient temperature a solution of di-tert-butyl dicarbonate(2.0 g, 9.16 mmol) in dry CH₂Cl₂ (20 mL) was added dropwise within 20min. After additional stirring for 1 h at ambient temperature, themixture was concentrated, redissolved in 20 mL water and extracted fourtimes with CH₂Cl₂ (10 mL). The organic layers were combined, washedthree times with brine, dried with MgSO₄ and concentrated to give 2.02 gof a colorless oil of 17 in an overall yield of 88.8% containing someimpurities of double protected species (20% determined from ¹H-NMR). Theanalytical data are in accordance with those reported in the literature(Ishida, M. et al. J. Am. Chem. Soc. 135, 12684-12689 (2013)).

¹H-NMR (300 MHz, CDCl₃): δ 5.17 (br, 1H, NHBoc), 3.63 (s, 4H, OCH₂CH₂O),3.56-3.47 (m, 4H, CH₂O), 3.35-3.23 (m, 2H, CH₂NHBoc), 2.86 (t, J=5.2 Hz,2H, CH₂NH₂), 1.51 (s, 2H, NH₂), 1.42 (s, 9H, CH₃); ¹³C-NMR (75 MHz,CDCl₃): δ 155.90, 79.03, 73.27, 70.08, 41.61, 40.21, 28.30.

N-Boc-N′-D-biotinyl-3,6-dioxaoctane,1,8-diamine (18)

To a solution of Boc-diamine 17 (109 mg, 0.44 mmol) and NEt₃ (81 μL,0.59 mmol) in dry DMF (5 mL), D-biotin N-hydroxysuccinimide ester (16,100 mg, 0.29 mmol) was added and stirred for 12 h. The solvent wasremoved, the residue resolved in CH₂Cl₂ (40 mL), washed with 20 mLbrine, dried over MgSO₄ and concentrated. Flash column chromatography(silica gel, CH₂Cl₂/MeOH: 99/1→93/7) gave compound 18 (0.128 g, 93%).Analytical data matched the literature (Braun, M. et al. Eur. J. Org.Chem., 1173-1181 (2000)).

TLC (CH₂Cl₂:MeOH, 90:10 v/v): R, =0.37; ¹H-NMR (300 MHz, CDCl₃): δ7.35-7.23 (br, 1H. CONH), 6.77-6.19 (br, 2H, NH), 5.24-5.04 (br, 1H,CONH), 4.59-4.48 (m, 1H, CH), 4.40-4.28 (m, 1H, CH), 3.63 (s, 4H,OCH₂CH₂O), 3.58 (dt, J₁=J₂=5.4 Hz, 4H, CH₂O), 3.46 (dt, J₁=J₂=4.9 Hz,2H, CH₂NH), 3.32 (dt, J₁=J₂=5.4 Hz, 2H, CH₂NHboc), 3.22-3.12 (m, 1H,CH), 2.98-2.89 (m, 1H, CHH_(exo)S), 2.76 (d, J=12.8 Hz, 1H,CHH_(endo)S), 2.26 (t, J=7.4 Hz, 2H, CH₂CO), 1.82-1.61 (m, 4H, CH₂),1.46 (s, 9H, CH₃), 1.26 (m, 2H, CH₂); ¹³C-NMR (75 MHz, CDCl₃): δ 173.52,165.20, 156.94, 79.10, 70.03 (4C), 61.78, 60.30, 55.30, 40.55, 40.31,39.13, 35.64, 29.61, 28.35 (3C) 27.96, 25.46.

N′-Boc-aminooxyacetyl-N-hydroxysuccinimide ester (19)

1-ethyl-3-(3-dimethylaminopropyl)carbodiimid (227 mg, 1.8 mmol) andN-hydroxysuccinimide (190 mg, 1.65 mmol) was added to a solution ofN-Boc-aminooxyacetic acid (287 mg, 1.5 mmol) in dry DMF (10 mL) andstirred at ambient temperature for 12 h. The mixture was diluted by theaddition of H2O (10 mL), extracted twice with EtOAc, the organic phasedried over MgSO4 and concentrated under vacuum. The yellowish liquid wasused without further purification (352 mg, 81%). Analytical data matchedthe literature (Palaniappan, K. K. et al. Angew. Chem. Int. Ed. 52,4849-4853 (2013)).

¹H-NMR (300 MHz, CDCl₃): δ 7.84 (s, 1H, NH), 4.61 (s, 2H, CH₂), 2.82 (s,4H, 2×CH₂), 1.31 (s, 9H, CH₃); ¹³C-NMR (151 MHz, CDCl₃) δ 164.83,162.92, 156.41, 82.17, 70.48, 27.88, 25.39.

N-aminooxyacetyl-N′-D-biotinyl-3,6-dioxaoctane,1,8-diamine (15)

Boc protected diamine 18 (127 mg, 0.32 mmol) was dissolved in CH₂Cl₂ (4mL), TFA (1 mL) was added and the solution stirred at ambienttemperature for 2 h. TFA was removed and the remaining solid was driedusing high vacuum. The deprotected diamine was dissolved in a mixture ofdry DMF (3 mL) and NEt₃ (89 μL, 0.64 mmol). Hydroxysuccinimide ester 19(152 mg, 0.52 mmol) was dissolved in dry DMF (0.5 mL), slowly added tothe diamine and the resulting mixture was stirred at ambient temperaturefor 12 h. The solvent was removed and flash column chromatography(silica gel, CH₂Cl₂:MeOH, 99:1 to 93:7) gave boc protected hydroxylamineS2 (TLC=[CH₂Cl₂:MeOH, 90:10 v/v]: R_(f)=0.3). A final deprotection in25% TFA solution (CH₂Cl₂) followed by TFA removal gave deprotectedhydroxylamine 15 (102.2 mg, 71%).

¹H-NMR (300 MHz, D2O): δ 4.50 (s, 2H, COCH2O), 4.49-4.43 (m, 1H, CH),4.24-4.31 (m, 1H, CH), 3.54 (s, 4H, OCH₂CH₂O), 3.52-3.45 (m, 4H, CH₂O),3.33 (dt, J₁=J₂=5.3 Hz, 2H, CH₂NH), 3.24 (dt, J₁=J₂=5.4 Hz, 2H,CH₂NHboc), 3.21-3.14 (m, 1H, CH), 2.85 (dd, J₁=13, J₂=4.9, Hz 1H,CHH_(exo)S), 2.62 (d, J=13 Hz, 1H, CHH_(endo)S), 2.13 (t, J=7.2 Hz, 2H,CH₂CO), 1.65-1.36 (m, 4H, CH₂), 1.32-1.20 (m, 2H, CH₂); ¹³C-NMR (151MHz, D₂O) δ 176.79, 168.56, 165.14, 71.52, 69.26, 69.23, 68.70, 68.44,61.93, 60.09, 55.20, 39.52, 38.67, 38.50, 35.26, 27.68, 27.52, 24.97;ESI-MS (m/z): [M]⁺ calcd. for C₁₈H₃₄N₅O₆S, 448.22; found 448.21.

Example 29: Synthesis of CF-Tub-Tag Peptide 13

CF-Tub-tag peptide was synthesized by standard Fmoc-based chemistry in alinear synthesis on an Activotec peptide synthesizer followed by manualcoupling of 5(6)-carboxyfluorescein.

0.1 mmol of Fmoc-L-Glu(tBu)-Wang resin (subst: 0.58 mmol/g) was added toa reaction vessel and synthesis was performed with five fold amino acidexcess. Coupling was achieved by HOBt/HBTU/DIPEA addition. After thefinal amino acid coupling, the fluorophore was coupled in a doublecoupling procedure with 5 eq of 5(6)-carboxyfluorescein, HOBt, HBTU andDIPEA in DMF for 1 h. The peptide was cleaved off the resin by additionof TFA/DTT/Tis/thioanisol (95/2/2/1) within 4 h. Subsequently, thecleavage cocktail was evaporated by N2-flow and the peptide wasprecipitated by the addition of ice cold diethyl ether. The precipitatewas spun down, dissolved in water and purified by preparative HPLC(method D). The peptide was obtained with a yield of 8% (16 mg, 8 μmol);molar mass peptide=1850.6 Da; ESI-HRMS (m/z): [M+2H]²⁺ calcd. 926.3165;found 926.3065.

Example 30: LC-UV at 220 nm, 10 to 100% of Acetonitrile in WaterContaining 0.1% TFA on a RP-C18 Column

See FIG. 28

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The invention claimed is:
 1. A method for the production of apolypeptide comprising (a) introducing or adding at the C-terminus of apolypeptide a recognition sequence for tubulin tyrosine ligase; and (b)contacting the polypeptide obtained in step (a) in the presence oftubulin tyrosine ligase and a tyrosine derivative under conditionssuitable for the tubulin tyrosine ligase to tyrosinate said polypeptidewith said tyrosine derivative.
 2. The method of claim 1, furthercomprising (c) conjugating a moiety to said tyrosinated polypeptideobtained in step (b).
 3. A method for the production of a polypeptidecomprising (a′) introducing or adding at the C-terminus of a polypeptidea recognition sequence for tubulin tyrosine ligase; and (b′) contactingthe polypeptide obtained in step (a′) in the presence of tubulintyrosine ligase and a tyrosine derivative conjugated to a moiety underconditions suitable for the tubulin tyrosine ligase to tyrosinate saidpolypeptide with said tyrosine derivative conjugated to said moiety. 4.The method of claim 1, wherein the recognition sequence for tubulintyrosine ligase has at least the amino acid sequence X₁X₂X₃X₄ (SEQ IDNo: 11), wherein X₁ and X₂ is any amino acid, X₃ is E, D or C and X₄ isE.
 5. The method of claim 1, wherein X₂ is G, S, A, V, or F.
 6. Themethod of claim 1, wherein X₁ is E, D, A, K, or P.
 7. The method ofclaim 1, wherein the recognition sequence is EGEE (SEQ ID No. 2).
 8. Themethod of claim 1, wherein the recognition sequence is VDSVEGEGEEEGEE(SEQ ID No. 3), SVEGEGEEEGEE (SEQ ID No. 4), SADGEDEGEE (SEQ ID No. 5),SVEAEAEEGEE (SEQ ID No. 6), SYEDEDEGEE (SEQ ID No. 7), or SFEEENEGEE(SEQ ID No. 8).
 9. The method of claim 1, wherein said polypeptidecomprises a linker sequence preceding the recognition sequence for thetubulin tyrosine ligase added in step (a).
 10. The method of claim 1,wherein said moiety conjugated to a tyrosinated polypeptide is acarrier, a polypeptide, a detectable label, a chemical compound, anucleic acid, a carbohydrate, or a lipid.
 11. The method of claim 10,wherein the polypeptide is an antibody or fragment thereof selected fromthe group consisting of a monoclonal antibody, chimeric antibody,humanized antibody, human antibody, scFv, a DART, domain antibody,nanobody, an adnectin, an affibody, an anticalin, a DARPin, or anaptamer.
 12. The method of claim 10, wherein the detectable labelcomprises a fluorophore, an enzyme (peroxidase, luciferase), aradioisotope, a fluorescent protein, or a fluorescent dye.
 13. Themethod of claim 10, wherein said chemical compound is a small molecule,a polymer, or a therapeutic agent.
 14. The method of claim 10, whereinthe nucleic acid is DNA, RNA, or an aptamer.
 15. The method of claim 1,wherein the suitable conditions comprise a buffer containing anucleoside triphosphate, such as ATP, potassium chloride, magnesiumchloride, a reducing agent such as DTT.
 16. The method of claim 1,wherein the suitable conditions further comprise a pH-value in the rangeof 5 to
 9. 17. The method of claim 1, wherein the suitable conditionsfurther comprise a tyrosine derivative concentration in the range of 0.1mM to 10 mM.
 18. The method of claim 1, wherein the suitable conditionsfurther comprise a reaction temperature in the range of 1° C. to 70° C.or 19° C. to 37° C.
 19. The method of claim 1, wherein the suitableconditions further comprise a reaction time in the range of 5 minutes to4 hours or 1 hour to 3 hours.
 20. The method of claim 1, wherein saidtyrosine derivative contains an unnatural functional group forchemoselective or bioorthogonal modifications.
 21. The method of claim20, wherein the unnatural functional group is selected from the groupconsisting of terminal alkyne, azide, strained alkyne, diene,dienophile, alkoxyamine, carbonyl, phosphine, phosphonite, phosphite,hydrazide, thiol, tetrazine, alkene, cyclooctyne, electron-withdrawingsubstitutents, phenol-derivatives, nitriles (CN), carbonyls (CO), ornitro groups (NO₂).
 22. The method of claim 1, wherein said tyrosinederivative is a 2, substituted, 3-substituted or 4-substituted tyrosineor a tyrosine derivative substituted at the benzylic position.
 23. Themethod of claim 22, wherein said 3- or 4-substituted tyrosine derivativeis 3-nitrotyrosine, 3-aminotyrosine, 3-azidotyrosine, 3-formyltyrosine,3-acetyltyrosine, or 4-aminophenylalanine.
 24. The method of claim 1,wherein said polypeptide has a length of more than 19 amino acids. 25.The method of claim 1, wherein said polypeptide is a polypeptide otherthan tubulin.
 26. A method for installing a click chemistry handle tothe C-terminus of a polypeptide other than tubulin, comprising: (a)providing a polypeptide having at its C-terminus a tubulin tyrosineligase recognition sequence; and (b) contacting the polypeptide of step(a) in the presence of tubulin tyrosine ligase and a tyrosine derivativecontaining an unnatural functional group for chemoselective orbioorthogonal modifications under conditions suitable for the tubulintyrosine ligase to tyrosinate said polypeptide with said tyrosinederivative.
 27. The method of claim 26, optionally further comprisingconjugating a moiety selected from a carrier, a polypeptide, adetectable label, a chemical compound, a nucleic acid, a carbohydrate,or a lipid to said tyrosinated polypeptide obtained in step (b).
 28. Themethod of claim 13, wherein the synthetic polymer is PEG.
 29. The methodof claim 26 wherein said unnatural functional group is selected from thegroup consisting of terminal alkyne, azide, strained alkyne, diene,dienophile, alkoxyamine, carbonyl, phosphine, phosphonite, phosphite,hydrazide, thiol, tetrazine, alkene, cyclooctyne, F, Br, Cl, I,phenol-derivatives, nitriles, carbonyls, or nitro groups.
 30. The methodof claim 21, wherein the electron-withdrawing substituent is a halogen.31. The method of claim 30, wherein the halogen is F, Br, Cl or I.